23. Maginot Line: France
Taken from lessons learned from trench warfare in the Great War, the French fortified their borders with Italy, Germany, and Luxembourg with concrete underground structures leading up to World War II. The idea was that they’d created an impenetrable line of defense that the Germans would have to go around. The line connected via underground railways. It housed underground accommodations for troops complete with air-conditioned quarters. The Germans bypassed this French work of genius by entering the country through Belgium and the Netherlands.
22. 109th Iman Fortified: Russia
On the eastern edge of the former Soviet Union, the Soviets erected fortifications to protect them from Japanese attacks. The two nations pounded the land around this installation, but much of the original structure remains, half-buried in earth and plants, tagged by artists, and otherwise forgotten for over six decades. Still, the barbed wire stands guard just in case.
21. Saint Nazaire Submarine Base: France
On the north end of the Bay of Biscay, south of the English Channel, the French have a base specifically for submarines, leftover from the Nazi occupation. As the Germans churned out endless U-Boats, they needed someplace to park them. The base in Saint Nazaire served not only as a submarine pen but a place to house many Nazi activities. They kept dormitories, war offices, kitchens, an electrical plant, and a hospital. The French have maintained the site as a historic site. In one of the pens sits a French submarine, the Espadon, which tourists can check out while in Saint Nazaire.