The Troodos mountain range stretches across most of the western side of Cyprus. There are many mountain resorts, Byzantine monasteries, and churches on mountain peaks, and nestling in its valleys and mountains are villages clinging to terraced hills. The area has been known since antiquity for its mines, which for centuries supplied copper to the entire Mediterranean. In the Byzantine period it became a centre of Byzantine art, as churches and monasteries were built in the mountains, away from the threatened coastline. The mountains are also home to RAF Troodos, a listening post for the NSA and GCHQ.