Skrunda-1 belongs to a group of some 40 secret cities whose existence was a top-level national secret. They were created to hide manpower and weapons at strategic locations throughout the USSR.
Urban explorers have been sneaking onto these wild, forbidden islands just off the Helsinki mainland for years. Now, you too can go.
Late last year, we had the opportunity to visit yet another structure belonging to the first defensive belt of Lyon: Fort de Caluire, or Champignonnière de Caluire.
The deep, wet and unpredictable cave belongs to Krepost Sveaborg, a Russian-built landward defence zone of over 300 fortification structures in and around Helsinki.
The former state prison and would-be cultural center in the heart of Podgorica offers a fascinating glimpse into the criminal history of Montenegro.
Even today, just finding former nuclear missile base Vogelsang, hidden deep in East German forests, can be a challenge. But those who do are rewarded with a singular experience.
Built by the Nazis and seized by the Red Army, the now-derelict military base of Krampnitz Kaserne in the outskirts of Potsdam hides many mysteries, including one famously elusive eagle mosaic.
Fort Loyasse is a relic of a now improbable-seeming time when the biggest external threat to France was the then-fearsome military power of Austria.