Ancient serpentine sacrifice holder that has stood the test of time.

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

A fountain standing as a testament to a doomed alliance.

Terrifically morbid cemetary and site of famous Paracelsus' grave.

This medieval cathedral houses stained-glass windows featuring saints and pretzels.

This ancient Roman prison is decorated with an upside-down cross not as blasphemy but as saintly tribute.

A 2,000-year-old computer demonstrates remarkable engineering and astronomical precision.

Ancient catacombs form the foundation for this Rococo orgy of a church.

The stunning interior of this Gothic church is covered in ornate gold details.

A hidden three-foot-wide house separates these two regal churches.

This restored Portuguese cafe may well be the most beautiful place in the world to grab a Big Mac.

This controversial statue once honoured a Russian Field Marshall, before ultimately being dismantled in a push to remove symbols of Russian influence.

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

3,000 market stands in five former Zeppelin hangars.

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

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

The oldest housing complex in Riga is a mini timeline of architectural trends.

This enigmatic artifact remained buried in a churchyard for years.

Built to repay the sins of the father, this church is home to one of the most valuable works of Western art.

This 15th-century church houses priceless works of art from a range of Croatian artists.

The Roman city was the birthplace of various emperors and is home to one of the empire's most impressive architectural feats.

The world's largest wooden structure.

The final resting place of the great navigator, or maybe his brother.

Spain's largest bullring offers a unique glimpse at architecture and history.