On the Croatian side of the border with Bosnia, a Cold War airbase was cut into a mountain so that MiG-21s could be hidden, fuelled and launched from inside it. In May 1992 the army that built it blew it up, and the mountain has been quiet, mined and half forgotten ever since.
Bakić's 37-metre monument to the 1941 uprising once glittered with Swedish stainless steel above the forests of central Croatia. Now it is stripped, graffitied and carrying phone antennas, and a Netflix crew has filmed in it.
In December 1943 the 150 people of Imber were told to leave their Wiltshire village for a few months so American troops could train there. They never came back, and the village still stands empty inside an army firing range.
Kadykchan in Russia's far north-east was dug out of the permafrost by Gulag prisoners in 1943 to feed a power station. Then a mine explosion and a state decision left its flats empty and its streets silent.
Prora was meant to be a seaside holiday camp for 20,000 workers, a block of concrete 4.5 kilometres long on Rügen's Baltic coast. The war stopped it before a single holidaymaker arrived, and the shell went on to serve three armies before the luxury flats moved in.
Hidden in the Brandenburg forest north of Berlin, Vogelsang was a Soviet garrison town of up to 15,000 people, and for a few months in 1959 it held the first Soviet nuclear missiles in Germany.
Beneath Moscow there is said to be a second, secret metro for the country's leaders. Parts of the story are documented, and the rest is rumour that nobody in power will confirm.
Hidden in a Crimean mountain under 180 metres of rock, Object 221 was meant to run the Soviet Black Sea Fleet through a nuclear war. It was never finished, then looted, and now it may be back in military hands.
Hundreds of metres below a small town in eastern Ukraine lay one of Europe's largest salt mines, with a church, a concert hall and a football pitch carved from salt. Then the war reached it.
Cut into a mountain beside a narrow Crimean bay, Balaklava's secret submarine base was built to survive a nuclear strike and is now a museum.
Along France's Atlantic coast, Germany built vast concrete bunkers for its U-boats during the Second World War. Bombers could not break them, and today they are museums, art galleries, naval stores and silent ruins.
On the cliffs near Cap Gris-Nez, four huge concrete casemates once held German naval guns that could hit the English coast. One of them is now a museum, and the rest still stand in the fields.
Built in the Second World War with a runway half as long again as normal, RAF Sculthorpe became one of the biggest US Air Force bases in Britain, home to nuclear-capable bombers until it closed in 1992.
High in the Swiss Alps, a laboratory cut into the rock of the Jungfraujoch has measured cosmic rays, glaciers and the air since the 1930s.
Above Svalbard's Isfjorden, the ruins of Grumant mark a Russian and Soviet coal town that was evacuated in the war, shelled, rebuilt, and abandoned for good in the 1960s.
On the shore of Isfjorden, Colesbukta was the shipping end of a Soviet coal chain, and its ruins, a cabin museum and a lonely cemetery are still there.
On the steppe of Astrakhan Oblast, Kapustin Yar launched the Soviet Union's first ballistic missile in 1947 and went on to test its rockets, nuclear warheads and satellite launchers. It is still a military range.
Between Venice and the Lido, a small island once held plague ships, then a hospital and nursing home. It now stands empty, and the ghost stories told about it are much bigger than the documented history.
Behind an ordinary-looking bungalow in the Essex countryside, a 100-yard tunnel leads down to a three-level bunker about 125 feet underground. Built in 1952 as an RAF command centre, it became a regional government headquarters for a nuclear war, and is now a museum.
Before radar, Britain tried to hear the enemy coming. From the First World War to the early 1930s, concrete dishes and walls on the Kent coast gathered the sound of aircraft engines over the Channel. The best preserved stand on an island in a gravel pit near Dungeness.
Built in the late 1960s for a secret US-British radar that never worked, the buildings on Orford Ness were given a second life as a giant medium-wave transmitter. For nearly thirty years its masts carried the BBC World Service across Europe, and now the same site broadcasts Radio Caroline.
East Germany's only permanent amusement park closed in 2001–2002 after its visitor numbers collapsed, and its owner left for Peru. For more than a decade its Ferris wheel and dinosaurs rusted in the Plänterwald, and now the park is being rebuilt.
Teufelsberg is a hill built from the ruins of Berlin, over the shell of an unfinished Nazi college. On top, American and British listeners spent the Cold War eavesdropping on the East. Today its white domes are covered in graffiti.
Between 1943 and 1945 the Nazis dug into the gneiss of the Owl Mountains in Lower Silesia, using thousands of forced labourers to build seven underground sites. Nobody knows for sure what Project Riese, the Giant, was meant to be.
