Albanian Air Force hangar inside a mountain

"Also widely known as 'Gjadr' or 'Gjadër', Zadrima is located in the north west of the country, south of Shkodër (Skhodra), about 65km north of Tiranë. The airfield is unique in Albania in being built near a mountain. It was built to allow aircraft after landing to go into a tunnel under the mountain. The tunnels have a capacity of storing about 50 aircraft plus personel. As the airfield is located in the side ofthe mountain, the pilots have to be careful not turn when taking off as they can crash on the sides of the mountain. This airfield was built to minimise the threat from the Serbian Air Force entering Albanian airspace. Hence, the most advanced aircraft, the F-7 was based there, to counter any Serbian aircraft. Construction of the base began in 1969, but because of its complexity it wasn't finished until the mid 1970s. The first aircraft to use its runway landed on 10 July 1973, and the official opening was held on 15 March 1974. Regiment 5646 was established here with one squadron of F-6s, but in May 1976 six FT-5s arrived here and also the F-7A squadron from Rinas. On 16 October 1976, a second F-6 squadron moved to the base from Kuçovë. The home unit was later redesignated 4010 Regt. From April to November 1995 the base hosted Predator UAV systems operated by the USAF to monitor the conflict in Bosnia. On 12 March 1997, the base was stormed by local people and several buildings, including the control tower, were destroyed. Lack of funds prevented the base from being repaired, and flying operations ceased in 2000. It is now used as a storage facility for fighter aircraft withdrawn from service. No air force aircraft are permanently based there."
--www.aeroflight.co.uk