Some cities are so top-secret they can’t even be found on a map. Others are padlocked, hidden in the forest, or buried deep underground.

From Poland’s 800-year-old Wieliczka Salt Mines to America’s WWII mystery towns, SPYSCAPE explores some of the world’s most intriguing secret cities.

The Manhattan Project, US

In 1942, the US Army quietly began acquiring land in three remote areas: Oak Ridge, Tennessee; Los Alamos, New Mexico; and Hanford/Richland, Washington. Thousands of young workers arrived soon afterward, erecting prefabricated houses and industrial structures. The cities didn’t appear on any map and the US government didn’t acknowledge they existed although 125,000 people lived there. On August 6, 1945, when the US dropped an atomic bomb on Hiroshima, Japan, President Harry S. Truman revealed the purpose of the three cities and their cutting-edge work on The Manhattan Project that produced America's first nuclear weapons.

While you can't go back in time, you can visit the Manhattan Project National Historical Park, commemorating the Manhattan Project, which is run jointly by the National Park Service and Department of Energy.

Wünsdorf, Germany

Time does stands still in Wünsdorf, Germany, however, a one-time Nazi HQ hidden in a pine forest. The Soviets took over in 1945 without a shot fired. Some 75,000 men, women, and children moved into ‘Little Moscow’, about 25 miles from Berlin. It was the biggest Soviet military camp outside the USSR, with shops, schools, and daily trains to Moscow. Many residents were ordered to return home at short notice when the Soviet Union collapsed, however, leaving behind 98,300 rounds of ammunition, 47,000 pieces of ordnance, and 29.3 tonnes of munitions. The grand pool, casino, and concert hall are long gone, but the old soldiers’ barracks are being converted to modern apartments. Check online for information about guided walking tours.

Burlington, England

Up until it was declassified in December 2004, very few knew the UK had a 35-acre, underground site in Wiltshire to relocate 4,000 government staff in the event of a nuclear war or an invasion. ’Burlington’, as it is known, is an urban fortress within a 240-acre abandoned quarry, connected to the outside world through hidden entrances. Inside, there are purpose-built rooms to house the government and space for a bakery, hospital, and BBC broadcasting studios. While you can't poke around the local newspaper has posted eerie photos of Burlington. There is also video of the Ministry of Defense bunker posted online. Burlington wasn’t the only Cold War bunker, of course. Similar nuclear shelters were constructed worldwide from West Virginia to Bunker 42 in Moscow. 
‍

Portland, Oregon

Did Portland operate an underground city where men were kidnapped to work on ships? Historians disagree on what happened in the 1800s. Some believe a thirsty logger might stop at a tavern and wake up aboard a ship with a one-way ticket to Asia. Others note the tunnels connected Portland’s Chinatown former gambling and opium dens. The city’s network of tunnels runs from Old Town/Chinatown (hence the name ‘Shanghaiing’) into downtown Portland. Bar and hotel basements are also linked, as is the Willamette River docks. Why not explore the tunnels and decide for yourself.

The Rock of Gibraltar Stay-Behind Tunnels

Gibraltar, at the southern tip of Spain, hid an underground WWII city that could accommodate a 16,000-strong garrison with food to last 16 months. The British-controlled tunnels allowed Allies to run spy networks and protect the Rock’s strategic location next to the Mediterranean Sea. The tunnels hid a telephone exchange, a power generating station, a water distillation plant, a hospital, a bakery, ammunition magazines, and a vehicle maintenance workshop. The network stretched 34 miles (55km) and some sections remain open for guided tours. Overnight stays in a top-secret British spy base within the Rock are also allowed - but only 30 guests can visit the Stay Behind Cave each year.