The palace for King Gustav III was never completed, but the foundation remains tucked away in this city park.

A king's bloodstained shirt is among the gruesome collection of artifacts displayed below Stockholm's Royal Palace.

A plaque marks the house in Stockholm where the French philosopher René Descartes lived up until his death.

It is said that each of the white stones in the red facade of this medieval house represents the head of a murdered Swedish noble.

A rare surviving Victorian greenhouse designed specifically to house giant water lilies.

This Stockholm light tower can be controlled by anyone with a smartphone.

A hidden bathhouse in one of Stockholm's oldest and busiest neighborhoods is open to anyone who can find it.

This Hungarian castle was built out of cardboard and wood until it proved so popular that it got upgraded to stone.

A 19th century artistocrat's mansion, turned into a library, hidden in a modern library.

This lavish estate recalls the opulent history of Calcutta.

This Jewish bakery, among the last in the region, sells legendary sweets from a century-old storefront.

The topiary maze at the Habsburg hunting lodge.

Built to give thanks for the passing of a plague epidemic, this cathedral is a one-of-a-kind architectural hybrid.

The final resting place for the remains of 143 Habsburg royalty.

A small museum filled with over 1,000 clocks, and one particular clock calibrated to run until the year 9999.

The crypt of the imposing Stephensdom holds royal intestines and thousands of skeletons.

The beautiful baroque library of the Hapsburg empire.

This small museum is basically a time capsule of daily life in the Soviet Union.

This Russian diner is staffed entirely by twins.

One of the largest collections of socialist realist art shows the surprising depth of the official art of the Soviet Union.

For lovers of Soviet cinema, this museum is home to a vast collection of artifacts and costumes.

A monument to Malchik, a stray dog who lived in a Moscow metro station until his tragic death.

The avant-garde design was able to bypass strict Soviet regulations on architecture.

Thirteen sculptures in central Moscow graphically depicting vices of the modern world.