This ''hidden'' 19th-century bridge played a simple, yet important role during the Spanish-American War.

This limestone cave offers an incredible view of the Río Grande de Arecibo valley.

A traditional American farmhouse plopped in the middle of a Piccadilly courtyard.

Wedged between two buildings at the Great Ormond Street Hospital is this secret music installation.

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

One part local history, 99 parts gruesome haunted house.

Eighty million natural history specimens call this gargantuan museum home.

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

If your school was decorated with trippy graffiti, served ambrosial coffee, and was frequented by mimes, it might have been similar to this groovy cafe.

Since 1874, this macabre collection has developed into a museum devoted to Scotland Yard's mementos of dastardly deeds.

This five-star hotel was originally a swanky parking garage.

One of the figures in this Celtic sculpture continues to puzzle archaeologists.

A collection of machines designed to break things for science.

Classic game cookery takes center stage at what's widely considered London's oldest restaurant.

A museum wholly devoted to juvenescence.

Lovers proclaim their unbreakable bond by leaving their names on locks fastened onto the Shoreditch fence in East London.

Two plaques commemorate the site of Shakespeare's first theatre.

The pioneer of psychoanalysis spent the final year of his life here, still seeing patients on that famous couch.

A mysterious pair of mice eating a piece of cheese is London's smallest public sculpture.

Artists and musicians now rule over this former rail station.

Repository for more than 22 million pickled specimens.

This wildly-tiled artist's palace is a living and growing account of the creator's life, loves, and labors.

A historic London pub with prison cells in the cellar and a "spy room" on the second floor.

The anatomical-pathological collection of a man who changed surgery.