A hands-off space for graffiti artists to hone and display their skills.

A 1,215-foot tunnel transports pedestrians beneath the River Thames.

Nicolas Schöffer's massive interactive sculpture was assembled in 1961 and brought back online in 2016.

This giant urban staircase was built to keep the city's brave fighting men from getting waylaid in the red light district.

A marble Lucifer hides behind the pulpit of this Gothic cathedral.

This remarkably well-preserved Egyptian plinth is pretty well traveled for a giant piece of stone.

The largest underground lake in Europe.

Welsh literary history is preserved in the delicate pages of these medieval manuscripts.

Originally meant to hold a statue of King William IV, this support sat empty for years. Today, it hosts a rotating cast of public artwork.

An aptly-named street near the birthplace of the modern LGBT rights movement.

Kings Cross Station pays tribute to its role in Britain's best-selling book series.

A granite plane marks the site where a French aviator completed the first airplane flight across the English channel.

The somber sculptures commemorating Irish Famine on the river Liffey in Dublin.

A public work of art that also provides some relief from the summer heat.

Strange rumors surround the artist who created these solemn metal guard dogs.

Martin Bricelj Baraga's monolithic sculpture measures the blueness of the sky, and changes color to match it.

A trough of 700 strange bronze faces runs through a narrow alley in Ljubljana's old town.

A whimsical bridge adorned with decorative dragons.

This abandoned Slovenian military barracks has become a punky-political art squat.

This mural honoring a drowned village has become a symbol of Welsh pride and patriotism.

A 19th-century funicular railway shuttles visitors up this surprising sea cliff to one of the world's largest camera obscuras.

The longest and tallest aqueduct in Britain can actually be sailed across.

A real-life Professor Snape once taught in this Welsh university building, which students of course nicknamed “Hogwarts.”

The first piece of public art dedicated to LGBT rights.