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.
A railway worker picked up a stone in the sand in 1908, and within a few years a German-style town of ballrooms, ice and champagne stood in the Namib. The diamonds moved south, the people followed, and the dunes now fill the houses.
Built on a river island in the 1830s and 1840s, the fortress at Brest hosted the treaty that took Russia out of the First World War, held Polish opposition leaders in the 1930s, and was attacked in the first hour of Operation Barbarossa. Its ruins now stand inside a vast Soviet-era memorial complex.
