One of few vertical lava tubes in the world accessible by foot.

Eat the ultimate iteration of Portugal's most beloved pastry.

This glass skywalk offers vertiginous views down the volcanic cliffs to the beach below.

An intricately decorated tiny place of worship.

The largest fountain in Bratislava.

This spaceship sculpture in the middle of the Slovakian capital looks like it just crash-landed.

This crumbling medieval basilica once attracted pilgrims by the thousands to collect a miraculous dust that formed above the saint's tomb.

The ancient latrines of the Greeks, in all their public glory.

These tombs were built into the side of a mountain so that ancient angels could reach the dead.

One of the best-preserved medieval streets in Europe.

This secret coastal village is studded with pastel-colored houses all piled on top of one another.

A minotaur, a labyrinth, and a dubious restoration pull in visitors from around the world.

An 800-year-old island castle in Guernsey's main harbor.

One of the world's smallest prisons boasts just two small cells.

The first island in the world designated a light-pollution-free astronomical observation point.

Greenland's first shopping mall also hosts the country's government.

The remains of St. Lucius of Chur were said to be kept in this crypt for several centuries.

The world's largest second-hand graces a clock surrounded by constantly changing flower beds. 

This celebration of Latvia’s freedom and independence avoided demolition over half a century of Soviet occupation.

This charming Latvian lane doubled as Baker Street on the Soviet Union’s version of Sherlock Holmes.

The reconstruction of this prominent building fulfilled a long-written command.

Latvia's symbolic mountain-shaped national library is home to millions of cultural tomes.

A century-old prison in the heart of Vilnius is now a lively bar, dance club, and artist residency.

Over time, this castle grew to encompass the entire island.