With overtourism dominating the headlines and the onslaught of photos on social media it’s easy to feel that visiting somewhere without the crowds is something of a pipe-dream. But there are still plenty of places that you can travel to and have wholly, or almost all, to yourself. From booking a private island in Belize to bagging a space to explore Vietnam's most incredible cave system, here are 15 amazing places that only a handful of people get to visit.

If two year waiting lists don’t daunt you then read on. Currently only one operator, Oxalis, runs trips into the Hang Son Doong caves and they cap visitors at just 500 people per year. Those lucky enough to get in, will find themselves enveloped in a strange world, for even in a country blessed with countless caves, the -million-year-old Hang Son Doong are something else. Located in the Phong Nha-Ke Bang National Park, at their highest point the caves could fit a 40-storey skyscraper and at their widest point a 747 could glide through.

In fact, the Hang Son Doong cave system is so massive that it even creates its own weather system. And it doesn’t stop there. Inside you’ll find the biggest stalagmites in the world (a mighty 80m high), a tangle of jungle plants that have invaded the interior, an underground river that gurgles through the chasm, and, most bizarre of all, tennis-ball sized “cave pearls” – which are actually calcium deposits – that are scattered across the cave floor.

Known to many Italians as "the island that doesn't exist", Montecristo's nickname highlights just how few people have set foot on the island. In fact, until 2008 Montecristo wasn’t open to tourists at all and things haven’t got much easier in the decade since. The island accepts visitors just twice per year – between April 1 and 15, and from August 31 till October 31 – and into that slender timeframe only 1000 people are allowed to squeeze in. On top of that, many permits are reserved for students, while groups of 40 or more people get priority over individuals when applying.

But just why are people clamoring to visit a tiny island 40 miles off the coast of Italy? The answer is treasure. Montecristo (which is rather conveniently diamond-shaped) became immortalized in popular culture as the site of hidden treasure in Alexandre Dumas’ novel The Count of Monte Cristo. That pirate loot may be mythical but visitors today will find another bounty: a rich history, which has seen everyone from Turks and Greeks to Catholics and Romans pass by, and a fiercely protected environment that's home to a number of endangered species.

The Landmark Trust is no stranger to oversubscribed properties. Its host of spectacular and often quirky historic buildings are unsurprisingly popular with people looking to book a self-catering staycation with a twist. But even among such a well-curated collection of properties, Clavell Tower is something else. With a 19-month waiting list this place is a hot contender for the UK’s most in-demand holiday home. Prepare to put in some rather intense forward-planning and a stay here could be yours – and you’ll be pleased to hear that it's rather affordable too.

So what’s all the fuss about? Well, for a start Clavell Tower has a rather intriguing past. Built in the 1830s as a folly by Reverend John Richards, the property later became a coastguard lookout and then an observatory. But it's more than just history here, the four-storey tower is strikingly situated overlooking the sea at Kimmeridge Bay in Dorset – in fact, it’s right on the beautiful stretch of coastline that once coaxed the inspiration out of Thomas Hardy and P.D. James. And let’s face it, who can resist the idea of sleeping in their very own tower?

A journey to Gheralta's cave churches isn't an undertaking for the faint-hearted. These thirty-odd churches are incredibly remote, smuggled away in northern Ethiopia and carved into soaring sandstone cliffs which rise some 2580m above the dusty plains. To get to the churches requires hiking through slot canyons, free climbing almost-sheer rock walls and shuffling along cliff edges – all without a support rope in sight. It’s a journey that’s strenuous, and at times terrifying, but visiting these churches is an experience like no other.

Dating back over a thousand years, making them even older than Ethiopia’s famous Lalibela, the churches were carved away at such a lofty height to protect them from raids and to bring worshippers closer to heaven. While the churches' situation is astounding – graced with panoramic views of the surrounding mountains and scorched earth below – their interiors are also magnificent. Inside many of the churches are walls and pillars awash with frescoes, none more so than the small but exquisitely decorated Abuna Yemata Guh.

Ever dreamed of a castaway experience? Well you can now book your very own private island on Airbnb. Set off the coast of Belize, Bird Island, ticks all the Robinson Crusoe boxes: a little slice of paradise surrounded by limpid turquoise waters with not another soul in sight. The owner drops guests off at the island, which currently can sleep up to six people, and the self-sufficiency starts there. Bird Island does have drinking water and electricity (powered by solar and wind) but with no other inhabitants there, guests need to bring everything else they might need with them.

But fending for yourself is all part of the appeal and is a pretty small price to pay for undisturbed tranquility and for being surrounded by coral reefs that you can explore to your heart's content. So what's the catch? Booking your stay. While the price is £376 ($491) per night for the whole island, at our last check Bird Island was booked up well into 2020. Cancellations do sometimes happen, however unsurprisingly these are rather rare events.

As the Japanese proverb goes “A wise man climbs Fuji once. A fool climbs it twice” but get your timing wrong and you won’t be climbing it at all. The official climbing season is restricted to just a slim section of the year, from 1^st July until 31^st August, a timeframe that rules out visitors who want to see Japan in its loveliest seasons of spring’s cherry-blossom or autumn's golden hues. Outside the climbing season, the hike is only suitable for the most experienced climbers, with almost all facilities closed and the conditions at their most treacherous.

The climb to Fuji's summit is hardly a walk in the park at the best of times. The six-hour clamber from the fifth-station – which requires a five-hour hike to reach in itself – takes place at dawn when temperatures drop well below freezing and sudden storms near the summit aren’t as rare as you might like to think. But the hard trek is certainly worth it, few experiences in Japan can compete with the thrill of standing on the country’s iconic roof gazing across the landscape as a new day rolls in.

To many people the Seychelles spell out paradise, yet for the remote Outer Islands group paradise seems almost an understatement. Of this archipelago, the most remote is the untouched Aldabra Island, which is situated more than 100km from Mahé. As a UNESCO World Heritage Site and nature reserve, the island's environmental value is so weighty that David Attenborough described it as one of the world’s greatest natural treasures and scientists view it as a baseline for what Earth once looked like.

A whopping six tonnes of marine biomass per hectare encircle the island, thousands of migratory birds flock there and it's the only place on Earth where reptiles – represented by over 150,000 giant tortoises – still dominate the ecosystem. Visits are restricted to scientists and volunteers and, as there’s no boat or air service, a handful of wealthy visitors who can fork out for a private yacht or flight. All visits must be approved by the Seychelles Islands Foundation and even then sometimes the island is off-limits due to the area's fluctuating piracy risk.

Hidden in the remote northern foothills of the Maya Mountains, one of the most fascinating sites in Belize lay completely undiscovered until 1989. The three-mile-long Actun Tunichil Muknal cave system is more than just a series of rock-hewn formations, this is the site of Mayan remains that date back more than a thousand years, with bones and fragments that are thought to date between 250 and 909 A.D. Referred to by locals as the “place of fear”, this was once believed to be the site of ritual human sacrifice.

If the contents of the caves make you feel uneasy, it’s unlikely that you’ll derive much comfort from the journey you’d need to undertake to reach the site. Shut off for centuries, the caves have only been accessible to visitors, on official tours, for the past ten or so years and the journey there is challenging to say the least. The excursion is kicked off by a strenuous hike through humid rainforest, followed by a swim across a potentially crocodile-infested river, and finally ends with a descent into the cavernous mouth of the cave system.

It’s been quite the year for Frogmore House. Selected as the location for Harry and Meghan’s engagement interview and later for the couple’s wedding reception, 2018 has added another glimmer of limelight to add to the property’s illustrious history. Built in the 17th century, Frogmore House became a royal residence when George III purchased it for his wife Queen Charlotte in 1792. In fact, much of the striking 35-acre gardens nod to this time, thanks to Queen Charlotte who sculptured them with lakes, bridges and glades.

In the centuries since, successive members of the Royal Family have left their mark on the house and gardens: Queen Victoria’s Tea House; the 18th-century lake; the white-marble Indian Kiosk; and the artworks in the house. However, although it’s no longer a permanent royal residence, access to Frogmore House is highly restricted with the house only opening to individual visitors on three Charity Open Days in June each year. Groups might have a bit more luck, as pre-booked groups of over 15 people can gain access during August. Or why not try one of these other royal residences? 

Viewed as the pinnacle of luxury travel when it launched in 1912, now a handful of wealthy people are being offered a once-in-a-lifetime chance to visit the Titanic. Experience company OceanGate are launching the first manned exploration of the site since 2005, with June 2019 marking the beginning of its six-week expedition. The price tag is high – tickets for the first trip cost £80,500 ($105,129) – but this certainly isn’t a luxury vacation, it’s a proper scientific mission where each week nine guests will be donning the cap of “mission specialist” and actively aiding the research crew.

And the mission? To laser scan the wreck site to assess the rate of the ship’s decay and to capture the first ever 4K images of the site – something that will open the door to creating a virtual reality experience of the wreck. During the expeditions, the site will be visited in a purpose-built submersible that plunges more than two miles below the surface of the Atlantic. The mission is set to run annually after the 2019 trip, however given the rate of decay of the wreck, these voyages could soon become some of the last opportunities to visit The Titanic. Discover more sinister secrets of the Titanic here.

Travellers seeking a slice of wilderness have been increasingly looking to Greenland. And nowhere fits the wild bill better than the Northeast Greenland National Park, the largest protected area in the world. It’s utterly uninhabited, populated instead by musk oxen, orcas, humpback whales and polar bears. Aside from a handful of scientists that visit each summer, only the sealers and whalers from the village of Ittoqqortoormiit are allowed any access.

For the rest of us, the best bet is to view the park from the deck of a rarely visiting ship. Slightly more accessible is Ittoqqortoormiit: nestled between the park and the world’s longest fjord system, this remote settlement – a scattering of colourful houses with just 450 inhabitants – is breathtaking. Getting there isn't easy, boats can only reach the village in July and August, while the rest of the year the frozen sea limits travel to dogsled, skis or snowmobile.

The word “tsingy” translates as "the place where one cannot walk”, a name that indicates just how impenetrable this place can be. In fact, the Tsingy de Bemaraha – Madagascar’s most extensive plateau of limestone karst pinnacles – is one of the hardest to reach UNESCO World Heritage sites in the world. The area was pretty much inaccessible until the 1990s when an organisation began installing a series of suspension bridges, ladders and steel cables to navigate the thorny pinnacles.

Exploring the park may have become easier but getting there remains a challenge. Located on Madagascar's far-flung west coast, the ten-or-so hour dirt-road drive involves crossing two major, crocodile-infested, rivers, while in the six-month rainy season the road becomes an impassable quagmire. But the journey's worth it for the chance to climb the serrated needles of rock, explore the geological maze of erosions, and gaze down across the jagged limestone forest.

Saudi Arabia is another place that keeps its riches very much under-wraps. From the modern glitz of Riyadh and world-class Red Sea diving sites, to the ancient mud-brick ruins of Dir'aiyah and the desert-scattered rock-tombs of Mada’in Saleh, Saudi Arabia is undoubtedly one of the world's most fascinating countries to visit. And until recently, it was all but closed to travellers, with a ban on tourist visas and a strict policy that limited foreign travel to only those entering the country for work, business, or on a pilgrimage.

However, Saudi Arabia's tight travel restrictions are now starting to thaw. In April 2018 the often closed-off country rolled out a new visa scheme, allowing single-entry travel to the country to tourists for the first time. This also included allowing travel for women aged 25 years and over (younger women still need to be accompanied by a husband or male family member).

Of all the hard to reach and rarely visited places in the world – from the murky depths of the ocean floor to ice-sculpted mountain peaks – there's one final frontier that glimmers furthest from reach for most travellers. Space. No matter how many science fiction films you watch, the world beyond our planet still remains the most mysterious of places. Well, that's until 2020 at least, when plans for the first civilian trip into space are set to commence with aerospace companies Blue Origin, SpaceX and Virgin Galactic all jostling for first place in commercial space exploration.

Unsurprisingly being one of the first civilians in space comes with a hefty price tag, over 300 people have already reserved their seats for Virgin Galactic’s inaugural flight at the eye-watering cost of £153,100 ($200,000) per seat. Meanwhile, Elon Musk’s SpaceX is set to launch its first commercial flight in 2023, a private trip orbiting the moon which has been paid for by Japanese billionaire Yusaku Maezawa who will be accompanied by an elite guest list of eight artists who he's invited to capture the experience. 

If you’ve ever seen a photo of Bhutan's Tiger’s Nest, then no doubt the image has remained firmly etched in your mind. If you haven’t, then picture this: the world’s most breathtaking Buddhist monastery, glinting in gold, ochre and white and seemingly floating 900m above the Paro Valley floor as it clings to a craggy Himalayan cliff. For many, this description is the closest they will get. The journey there is an arduous one, across rickety bridges and through narrow passages as you tackle the steep 3000ft mountain climb to reach the lofty monastery.

But first, you need to get into Bhutan. To enter the country almost all nationalities require a visa, must book their trip with a Bhutanese travel operator, and must pay for a pricey all-inclusive package in advance. But it's worth it: Bhutan is no ordinary place. The last great Himalyan Kingdom offers more than the majestic Tiger’s Nest, it's home to fascinating architecture, spectacular festivals and a pristine environment of snow-dusted peaks and forest-cloaked mountains that are fiercely protected by law. Now find out what you're missing out on in the world's least visited countries too.