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

A black cat protests the City Guild in Riga's Old Town.

3,000 market stands in five former Zeppelin hangars.

A former Latvian headquarters of the brutal KGB secret police is now open as a grim reminder of their atrocities.

A 15-foot-tall statue of the head of the Sopranos family greets passengers at a train station in southeastern Lithuania.

This former KGB building is now a museum memorializing the people who suffered during the Soviet regime.

This magnificent Art Deco church is a reflection of Lithuania’s turbulent history.

An abandoned masterpiece of Soviet Brutalist architecture.

This micro-nation may be some sort of prank, but its constitution sure seems official.

Museum deep in the catacombs of St. Michael the Archangel Church is explored by touch, sound, and smell.

Ever-growing collection of devils in art.

Large, airy hallways hide within an impenetrable fortress that beckons urban explorers.

This unique structure allowed boats to bypass underwater mine barriers in the channel to enter the harbor.

These historic defenses ensured the city within would survive hundreds of years of occupations, sieges, and invasions.

A tiny church on a man-made island in the Adriatic.

An ancient knight and a symbol of the city's freedom.

When a supermarket opened up shop within a medieval building it became protected by UNESCO on a technicality.

There's a mini version of Iguazu Falls hidden in the Balkans, and it's got a rope swing.

This picturesque monastery at the base of a cliff is a peaceful oasis open to all visitors.

This abandoned airplane hanger is said to have once been a top secret launch facility.

Bridge that died in war and was resurected.

This surreal memorial/cemetery is a necropolis of crumbling stonework and puzzle-shaped headstones.

A former bank seized as a sniper vantage point during the Bosnian War is now a secret graffiti art gallery.

The only museum with its curator—and her pets—buried inside.