Vojni Aerodrom Željava

This former Yugoslav Air Force base (Vojni Aerodrom Željava), partly underground and completely abandoned, is one of Europe's most famous sites for lovers of modern military relics. It lies between Bosnia-Herzegovina and Croatia (17 km northwest of Bihać), at the foot of the Lička Plješivica massif (1,657 m above sea level). Access is via the 24-hour Izačić border crossing, and you'll need a flashlight to explore the interior. Željava was once one of the world's largest air bases. The project, launched in 1957 under the code name Objekat 505 ("Building 505"), was completed twelve years later at a cost equivalent to today's 7 billion euros. Commissioned in 1968, the base was designed to withstand a Soviet nuclear attack. Three squadrons of MIG-21s and F-84 Thunderjets - a total of sixty jet fighters - were housed in the underground facilities, along with all their equipment. The 3.5 km of tunnels could also accommodate a thousand soldiers capable of living independently for two months. But on May 16, 1992, it was burnt down by the Yugoslav army, which had passed into Serbian control.

Visit. The site is dangerous. The surrounding area is riddled with mines. Another concern is that the galleries are polluted by the chemicals released during the 1992 sabotage. The base has five runways, two in Croatia and three on either side of the border. The asphalt sections are safe. Nearby, the wrecks of two American-made aircraft remain: an F-84 Thunderjet used for reconnaissance and a Douglas C-47 Skytrain transport aircraft. Below Javornik-Tisov (1,200 m above sea level), four aircraft entrances open onto the galleries. Only part of the huge hangars is easily accessible. But metal debris, half-collapsed galleries and lack of lighting have turned the rest of the base into a labyrinth that is difficult to penetrate. Apart from the reinforced concrete structure itself, the underground section contains no interesting remains. Several guides from both countries offer a safe tour. Two in particular are recommended: Bosnian pilot Mirsad Fazlić, who served at the base in the 1980s and is a member of Bihać's "Željava" flying club; and Croatian historian Antonio Hodak, who runs the Thrill Quest agency specializing in Željava tours.