New Athos

Abkhazia is it's own country or part of Georgia, depending on who you are speaking with. This 3,300 square mile republic on the black sea has it's own mini-metro in New Athos known as the
"Subway in the Cave". Completed in 1975, this 3 station, 1291 meter line transports passengers in this resort town to the cave in Aspar mountain. According to the line's home page, the trains are converted miner's trollcars.

Abkhazia is described as
one of the most dangerous places on earth, but we're pretty sure the subway issafe.

Wikipedia page.