The art museum is decorated with creatively remodeled pre-Nazi swastikas.

Climb to the top of its spiral spire for spectacular views of Copenhagen.

The old observatory in Copenhagen has a spiral corridor used as a racetrack.

Pre-Nazi swastikas adorn the sculpted pachyderms flanking this brewhouse portal.

The de facto symbol of Copenhagen is this bronze fairytale which cannot seem to keep its head for very long.

Elevated freight railway turned wildly successful urban park.

What once sat in the world’s spotlight is today a largely disused ghost complex.

The 1852 novel "Uncle Tom's Cabin" lends its name to a subway station, a street, and several shops on the edge of Berlin.

The famous artist couple lived and worked here, in two different houses separated by a bridge.

A long-buried ancient ruin unearthed right in the middle of the city.

People have been living in the cave houses on this Italian hillside since the Neolithic era.

A cave in southern Italy adorned with thousand-year-old Biblical frescoes existed in obscurity until fairly recently.

The remains of an ancient city-state along the Silk Road.

This "tower of death" has acted as an observatory, a religious hub, and an executioner's lair.

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.