The world's biggest floating museum in Gothenburg, Sweden.

An old anti-aircraft cannon.

Swiss vineyards in a UNESCO heritage site.

Gargantuan home of Russian science.

The tallest hotel in Europe.

One of the oldest structures in Helsinki is this burrow grave that dates back to the Bronze Age.

Once the center of power for the region's various factories.

In the waters outside Helsinki, a tiny island once used as a military outpost now welcomes visitors.

The oldest arboretum on the Dalmatian coast doubles as the gardens of Kings Landing in "Game of Thrones."

Atop this electronic store resides a massive fighter jet.

This former hospital was once one of the oldest mental health facilities in Europe.

At this archaeological site, visitors can explore the ruins of the capital of the former Roman province of Moesia.

An 11th-century Byzantine church with medieval Serbian history and spectacular views.

Stone age urban planning.

This 14th century castle withstood years of battle but is now sliding off the hills into the Danube.

This statue of the "shiny uncle of Beppu" was erected in 2007.

The last surviving submarine from a strange chapter of Finnish history.

The "Mystery and Company of Merchant Adventurers" is an Elizabethan-era hangout in Moscow.

Home of the future Emperors of Russia.

World's largest bell sits on the grounds of the Kremlin in Moscow.

Former headquarters of the KGB.

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

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

An artificial date palm stands as a memorial to Warsaw's Jewish community.