This quiet, unassuming spot in Budapest was the birthplace of the bloody 1956 Hungarian Revolution.

A plaque hidden in the law faculty at Leiden University honors the first scientist to make liquid helium.

A tiny house showcases the busy life of a local gnome.

A striking memorial to the Jews of Leiden who were murdered during World War II is scattered throughout the city.

This early 19th-century graveyard is the final resting place of Vincent van Gogh's mother.

This 11th-century castle sits so low you can't see it behind the surrounding buildings.

People have been placing babies on these lilies for photoshoots since the Victorian era.

One of the Leiden's oldest pubs is also the birthplace of the Heineken star.

This Dutch art piece became a Russian icon.

The works of poetry's biggest names grace the walls of the city of Leiden, all carefully painted by hand.

Science meets wall art to highlight the beauty of famous mathematical equations.

Devious political maneuvering and four ancient, working telescopes are central to the world's second-oldest observatory.

A 'living museum' in Leiden, the oldest of its kind in the Netherlands.

A former plague hospital turned medical museum.

The metal leaves on this tree are engraved with the names of Holocaust victims.

A random tree outside a Budapest hotel has become a DIY shrine to the late singer.

A Trabant car, a kangaroo statue, and a plethora of plants take over this abandoned-factory-turned-bar.

Museum dedicated to the terror regimes of Hungary.

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

Built in 1870 at the bridge that connected Buda and Pest, this spectacular incline railway was almost lost forever during World War II.

A trail of iron footwear stands as a monument to the thousands executed along this riverbank during WWII.

Op-art architecture designed for happiness.

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

The beautiful baroque library of the Hapsburg empire.