This landmark Victorian folly rewards visitors with spectacular views over the Peak District.

A historic Georgian building and warm springs.

Once the largest unsupported dome in the world, beating out the Pantheon and St Peters in Rome.

A striking piece of street art in Southport depicting a much-loved racehorse.

Over 70 independent businesses have set up shop in this former Victorian department store.

This tiny watering hole claims to have the smallest bar counter in Europe.

Installed at a chaotic intersection, this gave London traffic cops a place to hang their heavy woolen coats.

These ornate arches show how the course of the River Thames has changed.

A living memorial to the trees London lost during the Great Storm of 1987.

The world's oldest optical museum is an odd collection where the exhibits look at you.

One of America's founding fathers lived in this London lodging between 1757 and 1775.

The medieval woodcut-style artwork chronicles life in medieval London.

This London pub hides a peculiar secret: a recreation of the rooms shared at 221b Baker Street by Sherlock Holmes and Dr. Watson.

A charming 17th-century alley is lined with secondhand bookstores and antiquarian shops.

This coffee shop lies hidden beneath a historic church.

London's smallest police station is barely the size of a phone booth.

These official units of measurement—including chains and perches—lie hidden beneath tourists' feet in a popular London hub.

Belfast's namesake river still winds below the city center, hidden from sight.

The only monument to name all of the passengers and crew who died on the RMS Titanic.

A giant sculpture of the legendary "Salmon of Knowledge" celebrates the return of fish to Belfast's River Lagan.

This massive monument has been telling the time for 150 years—at a slight angle.

Iceland: home to volcanoes, waterfalls and, apparently, Santa?

This excellent museum recreates the boom days of the herring rush in the "Atlantic Klondike."

The picturesque birthplace of Icelandic democracy is drenched in the blood of its brutal past.