No telescopes, no power, no gift shop: The Observatory of Chichen Itza, one of the world's oldest observatories, takes astronomy back to basics.

This irregularly shaped sea fortress has defended not one but three different sovereign states.

A whimsical bridge adorned with decorative dragons.

A World War II evacuation tunnel turned into a history display of Croatian state and people.

Where the lovelorn find a home for their sentimental keepsakes.

Home to three historic ships from the age of Vikings.

A new sculpture calls attention to climate change in the centuries-old city it threatens.

Two stone columns flank the grand Venice square, but there were supposed to be three.

This Venice bookstore has resigned itself to constant flooding by keeping its books in bathtubs and boats.

Destroyed Serbian army headquarters sits half crumbled in a largely revitalized Belgrade.

A pair of connected skyscrapers form this symbolic gateway.

One of the five gates into the fortress of to Shaniwar Wada was renamed to commemorate the 10th Peshwa of the Maratha Empire.

This Gothic-style church is reputedly built atop the remains of one of Jesus's apostles.

The painted and decorated towers of this Hindu shrine were once the tallest structures in one of the oldest cities in India.

Stockholm's narrowest alley is barely over two feet wide.

An ancient Viking runestone hidden in plain view in Stockholm's old town.

Is this statue at Naumberg Cathedral the fairest of them all?

An officers prison camp believed to be impregnable by the Germans saw over 30 successful escapes.

Retirement home for giant obsolete machines.

The 3,600-year-old archeological sensation is considered to be the oldest representation of the cosmos.

The monument honors the first (and for a long time, only) African-born philosopher to teach at a German university.

One of the most iconic neon ads of former East Germany.

A fairytale Gothic castle steeped in Nazi treasure conspiracy theories.

This centuries-old wooden wonder was built in less than a year and is one of Europe's largest timber-framed churches.