A Dutch passageway's artistic, aquatic-themed makeover pays tribute to the capital city's famed waterways.

One of Amsterdam's narrowest houses is located right across the canal from its widest.

The gorgeous entrances into the city's underbelly look more like grand halls than subway stops.

Former headquarters of the KGB.

This building holds the embalmed remains of the leader of the Bolshevik Revolution.

Underground monastery and fortress.

Take respite inside this jaw-dropping church while climbing the volcano where Georgia's Prometheus was once chained.

A cylinder monument with a spectacular vista commemorates a friendship that some say never existed.

This neon lit Georgian cave claims to hold the boulder Prometheus was chained to.

A literally moving statue of stacked metal giants just continually trying (and failing) to find love.

Fast food feels like fine dining at this award-winning modern Georgian building.

This architecturally eclectic fortress witnessed centuries of bloody turmoil, including the massacre of its ruling clan.

You'll find just about anything in this funky Tbilisi flea market.

The charmingly disheveled clock tower of Tbilisi's puppet theater.

A cluster of historic bathhouses built on the famed hot springs that gave the Georgian capital its name.

A rugged lava field dotted with molds of the ancient pines that were growing when the volcano erupted.

This Upstate New York park squeezes a lot of history into its two-acre triangular space.

Why have you never heard of the second most popular tourist site in New York?

This abandoned ironworks was once the most important military supplier in America.

This abandoned factory on the Hudson River once churned out a million bricks a week.

A 19th century hat factory still stands as a crumbling ruin in upstate New York.

The remains of what was once the world's steepest passenger funicular.

The largest known open fault in the United States is basically a giant natural refrigerator.

This stone gatehouse was once the entrance to a historic mountain resort, and it had a cameo in a cheesy cult horror movie.