The oldest floral clock in the world still functions today.

One of Scotland's earliest hydroelectric power stations.

An exceptional engineering feat that facilitates the migration of salmon upstream during their breeding season.

Several bricks indicate the various flood levels this crossing has survived over the centuries.

The longest staircase lock in Britain.

This uniquely shaped rock formation is one of Scotland's most iconic mountains and gives spectacular views in all directions.

This castle was established by the 4th Duke of Montrose and is connected to the Buchanan Clan.

The home of two of Scotland's most important artists has been reassembled in the Hunterian Art Gallery.

This neon sign is an homage to an Alfred Hitchcock film.

A warning against "the demon drink" adorns the northwest entrance of Glasgow Green.

A Paisley park where little has changed since its early 20th-century creation.

A mysterious ruin shrouded in more folklore than fact.

The narrowest house in the U.K.

Construction of this bridge was once described as an "act of violence" against a neighboring country.

Bridge that died in war and was resurected.

A former bank seized as a sniper vantage point during the Bosnian War is now a secret graffiti art gallery.

The oldest arboretum on the Dalmatian coast doubles as the gardens of Kings Landing in "Game of Thrones."

Longest fortress system anywhere in Europe.

The gardens and chambers of this Moorish citadel conjure memories of the Alhambra.

This Moorish fortress has guarded Málaga from the slopes of Gibralfaro hill for nearly a thousand years.

Now housed in a museum, this giant pink elephant stood in downtown Seattle for more than 60 years.

Montmartre's sole surviving windmill became an iconic landmark for 19th-century painters, artists, and bohemians.

If you look closely at the oldest bridge in Paris, you might notice hundreds of ugly faces leering from its sides.

An astonishingly accurate water clock that doubles as an hourly spectacle in this Berlin shopping area.