Hiding beneath the surface of a secluded section of Europe, a massive underground city exists with miles of tunnels filled with wine. Every “street” carries the name of a certain grape like Pinot or Cabernet Sauvignon. Visitors slowly drive cars or bikes through the maze, where normal traffic rules apply. Moldova’s Mileștii Mici proudly claims the title as the largest wine cellar in the world.

Moldova, sandwiched between Romania and Ukraine, holds a rich tradition in winemaking dating back thousands of years. Low hills, sun-drenched plains, flowing rivers, and moderate climate shaped by the Black Sea basin provide model conditions to grow grapes, rivaling other renowned vineyard regions across the continent. Once part of the Soviet Union, the country produced the most wine of all republics—every second bottle of wine consumed in the U.S.S.R. hailed from Moldova.

View Images Mileștii Mici holds almost two million bottles, earning recognition from the Guinness Book of World Records as the world's largest wine collection. Photograph by Alexander Spatari, Getty Images

“Although Moldovan wine is still looking for new markets worldwide and many people do not know about it, those who try it truly appreciate its real value,” says Viorel Bezede, Administrator at state-run Mileștii Mici.

So when an old limestone mine retired in the late 1960s, transforming its caverns into Mileștii Mici’s wine cellar made perfect sense. Temperatures in the subterranean space, which stretches about 150 miles, stays consistently in the mid-50s Fahrenheit, plus constant humidity creates ideal conditions for aging to perfection. Roughly half the space holds almost two million bottles, earning recognition from the Guinness Book of World Records as the largest wine collection in the world by number of bottles.