There's a variety of reasons that countries and cities can become no-go zones. Sometimes it's because of war or a natural disaster, or the decision of a drug lord to base an international cartel there. For some countries it was a quick look at the outside world followed by a decision that they didn’t want any part of it. We’ve put together a list of the most fascinating places around the planet that were once off-limits, but are now, sometimes tentatively, open to visitors again.

This UNESCO-listed walled city on Croatia’s stunning Dalmatian Coast is one of the most popular tourist destinations in Europe. In 2019, 1.5 million tourists squeezed through its narrow cobbled lanes – that's 36 tourists per resident. But when Croatia declared independence from Yugoslavia in 1991, the Yugoslav People’s Army attacked the city and laid siege for several months. Artillery set up on the hills overlooking the old city rained down shells, resulting in hundreds of deaths and destroying centuries-old buildings.

Thousands of people fled the city and for a time Dubrovnik was a ghost town. But after peace was declared in 1995, residents – and tourists – began to return. By the turn of the century visitor numbers had returned to their pre-war levels, and in 2011 the city got another boost when it was used as a film set for the immensely popular TV series, Game of Thrones. Today you're as likely to bump into someone looking for the streets used in Cersei’s famous 'walk of shame' as you are to come across a cute laneway restaurant selling seafood fresh from the Adriatic.

Timor-Leste (East Timor) has always been a place apart. While most of Indonesia, including the western part of the island of Timor, had been a Dutch colony, East Timor was claimed by the Portuguese. Shortly after the country gained independence from Portugal in 1975, Indonesia invaded and a brutal occupation ensued. For well over a decade the Revolutionary Front for an Independent East Timor (Fretilin) fought a guerrilla war with the Indonesian army, who enacted increasingly bloody crackdowns.

A UN-monitored referendum in 1999 saw 78% of the population vote for independence, after which the Indonesian army and pro-Indonesia militias drove hundreds of thousands of East Timorese into West Timor and wreaked havoc on East Timor’s infrastructure. A UN peace-keeping force was sent in and in 2002 the country finally became independent. Today, a nascent tourist industry is enticing visitors to discover its pristine beaches, rugged interiors and unique Portuguese-influenced culture.

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Karosta is a former Russian Imperial and Soviet naval base on the Baltic Sea in modern-day Liepaja in Latvia. It was built between 1890 and 1906 by Tsar Alexander III of Russia, and during the Soviet period served as a base for the Soviet Baltic Fleet. It became a closed military town, one of the most secretive in the Soviet Union. It was off-limits to everyone, including the people of Liepaja just a couple of miles away, who often came to the beach at Karosta to forage for amber that washed up on shore.

When Latvia gained independence in 1991 the Soviet army left Karosta, and parts of the city fell to ruin. Today, it has become an unlikely tourist attraction and a haven for artists. The military prison has been converted into a hotel and wedding space. The impressive Russian Orthodox Naval Cathedral, used as a gym and cinema during Soviet times, is holding services again. And graffiti artists have turned the old fort buildings crumbling into the sea into affecting canvases.

In 1988 Time magazine dubbed Medellin the most dangerous city in the world. It was the height of the Escobar years, when the notorious drug lord Pablo Escobar used the city as the base for a cartel that, at its peak, controlled around 80% of the world’s cocaine supply. Running battles with the police, political assassinations, bomb blasts and killings were commonplace. In 1991 the homicide rate reached a staggering 381 murders per 100,000 people, almost 40 times greater than the UN's benchmark for an epidemic of violence.

Escobar died 30 years ago, and the transformation has been staggering. In 2004 a series of infrastructure projects linked the poor, isolated settlements on the steep hillsides to Medellin’s economic centre. The economy came roaring back and in 2013 the city was named "the most innovative city in the world" by the Urban Land Institute. Today the city is reborn, making the most of its stunning location in a valley between two Andean mountain ridges, and tourists are discovering for themselves why Medellin is nicknamed 'the City of Eternal Spring'.

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The Khmer Rouge only ruled Cambodia from 1975 to 1979, but in that short time approximately two million people lost their lives. Their brutal leader Pol Pot declared the nation would start again at ‘Year Zero’, emptying the cities, abolishing money, private property and religion and forcing everyone to work on rural collectives. Anyone considered 'intellectual' was executed, while others died of starvation, disease and overwork when the social experiment inevitably failed. The country is littered with ‘killing fields’, where the victims were buried in mass graves.

The regime ultimately collapsed when neighbouring Vietnam invaded, establishing an occupation that would last a decade. The Vietnamese withdrew in 1989 and in the years since, Cambodia has become a popular tourist attraction, thanks particularly to the stunning Khmer ruins at Angkor Wat. Reminders remain of the terrible times under Pol Pot, including the Tuol Sleng Genocide Museum and the Memorial Stupa, both in capital city Phnom Penh. One of the most significant killing fields can be found at Wat Thmey near Siem Reap.

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The Maldives welcomed its first tourists in 1972. Aware that most of its islands were tiny and fearful of too much foreign influx and influence, the government implemented a ‘one resort, one island’ policy in 1978. These resorts were largely built on uninhabited islands, and travel to the more populous islands like Hithadhoo or Fuvahmulah was very challenging and very unusual.

It's only since 2009 that locals on inhabited islands have been allowed to build guesthouses, where tourists can stay among the local population. Intrepid travellers now have the opportunity to visit islands that were previously out of bounds, and experience more authentic island life in the Maldives. These islands still take some getting to, often on board one of the wooden cargo ships called 'vedis' that sail down from capital city Male carrying supplies and passengers.

Albania spent much of the latter half of the 20th century isolated from the rest of the world. Enver Hoxha, the country’s communist ruler, spurned all the world’s major powers and became so paranoid about invasion that he practically bankrupted the country by building concrete bunkers along every major road, border and seafront. Estimates vary on exactly how many bunkers he built – from 170,000 to 750,000 or more – and each one cost roughly the same as a two-bedroom apartment.

Hoxha died in 1985 but the bunkers remain. Some have been converted into dwellings, others have become tiny restaurants, cafes or art galleries. Many have been turned into works of art by graffiti artists. Since transitioning to democracy in 1990 the country has also become a popular tourist destination, offering Mediterranean beach resorts like Ksamil (pictured), stunning mountain hiking and big city thrills in Tirana, all at a much more affordable price than its big-name neighbours.

Sperrgebiet is a diamond-rich area in the southern Namib desert in southwestern Namibia. It was closed to the public after a railway worker called Zacharias Lewala found a diamond at Kolmanskop in 1908. Sperrgebiet means 'prohibited area' in German and the whole area was shut off from the outside world until the early 21st century. It was a secretive place of rich diamond mines, treacherous sand seas and mysterious folk tales.

In 2004 the Sperrgebiet region was declared an 8,500-square-mile (22,000sq km) national park. Known as Tsau Khaeb, the park was tentatively part-opened to visitors who discovered abandoned mines, eerie ghost towns swallowed by sand and the skeletons of ships wrecked along the jagged coastline. The park was quickly recognised as a top biodiversity hotspot, and its swirling sea fog supports more endemic species of succulent than can be found anywhere else on earth. It is home to Namibia’s first Marine Protected Area too, where whales, dolphins, fur seals and vast seabird colonies abound.

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Bhutan is the quintessential hermit kingdom, cut off from the rest of the world for centuries and fiercely protective of its culture and traditions. It sits high in the Himalayas, tucked between China and India, and maintains a heavy emphasis on peace and harmony measured as Gross National Happiness. When tourists were finally let in during the 1970s it was under the strictest of conditions. The administrative challenges of visiting were immense, and in 1974 only 287 tourists were allowed into the country.

Between 2012 and 2016 the number of visitors to the kingdom increased by 24%, but Bhutan retains a strong sense of its own identity. There are no traffic lights, government employees must wear traditional clothing (a gho robe for men and kira dress for women) during work hours and watching TV was only reluctantly allowed in 1999. Those lucky enough to visit must pay a hefty daily fee, but the rewards are immense: breathtaking natural scenery, extraordinary Buddhist temples and a culture in which centuries-old traditions are still a part of everyday life.

After the Second World War, Germany was split in two by the Soviet Union and the Western Allies. The capital of Berlin was divided into east and west and was separated in 1961 by the notorious Berlin Wall. Neighbourhoods were divided, as, sometimes, were families. Travelling between the two sectors soon became increasingly difficult and, in the end, impossible. The crossing at Checkpoint Charlie was like something out of a spy novel, and more than 600 East Germans lost their lives trying to cross the wall and escape.

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Today Checkpoint Charlie is a popular attraction where tourists pose for photos with people dressed as Soviet and American guards. There’s a McDonald's on the corner opposite and visitors can walk freely between the two 'sectors'. Sections of the Berlin Wall remain, a sombre reminder of more restrictive times, but generally East Berlin has embraced the freedoms and opportunities that came when the Wall fell in 1989. Today it is home to some of the city’s most exciting clubs, bars and restaurants, as well as museums and galleries.

Soweto is a township on the southwest edge of Johannesburg. It was set aside by the white South African government for black labourers who flocked here from rural areas between the First and Second World Wars. Conditions were often very poor and the slums here became a hotbed of anger and insurrection against the apartheid regime, culminating in the Soweto Rebellion in 1976, which was partly triggered by government insistence that the Afrikaans language be used in Soweto's schools. Vilakazi Street, in the heart of the township, was once home to Archbishop Desmond Tutu and Nelson Mandela.

Since the end of apartheid in 1990 conditions have improved in Soweto, but most of the residents still have to travel into Johannesburg for work. However, tourism is now a growing source of income, with visitors flocking from all around the world to visit the museum in Nelson Mandela’s old house. There’s also a growing foodie and music scene. Ubuntu Kraal Brewery, Soweto Theatre and Locrate Market are popular drop-in spots, while a bungee jump from the decommissioned Orlando Power Station is a must for the more adventurous.

Read on to learn about the US cities that are having a revival after being down on their luck