Ancient barriers wrap around what was once an important stop along the Silk Road.

Light still pours into the ruins of this ancient Islamic observatory.

Once a bustling fishing port, this semi-ghost town is now more than 90 miles away from the shore.

The Avenue of Mausolea is a series of grand palatial tombs.

The highest rapid transit station in the world.

Climb a steep hill in 90 seconds on the second-oldest urban subway in the world.

Diego Rivera hid various people and symbols in his first large-scale mural project.

One of the most beautiful bookstores in the world hides a neo-Gothic interior behind an art nouveau facade.

Spanish architects used seized Muslim gravestones to rebuild parts of the fortress.

The first modernist church in Europe.

An exquisite Baroque church in Vienna's old town.

Baroque celebration of the end of the Great Plague of Vienna.

This dome-shaped mountain boasts amazing views and has a rich religious history.

This striking royal residence is the largest Renaissance-style castle in Scandinavia.

Giant eggs, walls of bread, and nightmare surreality mark the largest collection of works by Salvador Dalí.

Three bridges and one giant canyon make up this fantastic Spanish settlement.

Historic medieval fortified city in southwest France.

Outstanding taxidermy dioramas showcase the grandeur of the continent's wildlife with spooky realism.

The Polish capital has had a deep connection to its guardian mermaid for almost a millennium now.

Stare out over the lagoon and beyond from this 10th-century campanile on the island where the city of Venice began.

Museum dedicated to "the man who moved the Earth."

This exceptionally well-preserved ancient marvel also houses a small museum dedicated to Jordanian folk tradition.

In a city that boasts four separate inclined cable railways, this is one of the busiest funicular lines in the world.

The once forbidden "secret cabinet" of erotic art from excavations of Pompeii and Herculaneum.