Sazan is the largest island in Albania, with an area of 5.8 square kilometres, was a Soviet military base, and perhaps even a chemical weapons plant.  In 2015  it made the newsfollowing decades of silence, when it was eventually opened to the public. You can spend a day pottering through tunnels and bunkers designed to survive a nuclear assault!

An interesting side effect–the position of Sazan, where the Ionian and Adriatic Seas converge, offers the Albanian mainland a subtropical climate of differing weather conditions for being so nearby.