Murals of the wild parties once held on the frozen River Thames.

The last remaining example of the boatmen's perches that once dotted the south bank of the Thames.

The London statue that imitates passersby.

A labyrinth hides in plain sight at each of the city's 270 Tube stations.

An alleyway plaque is all that remains of the independent Texas' envoy that forgot to pay their rent for over a century.

An easily overlooked stretch of ornate window fronts and gaslight lamps that could be right from the pages of Dickens.

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

Claiming to be the oldest hat store in the world, this historic haberdashery had a hand (and a head) in the creation of the Bowler.

The final resting place of a German diplomat's beloved companion.

Several plaster noses are hidden in plain sight around London's Soho neighborhood.

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.

A celebration of capitalism in Midtown.

The 5.5-mile ring of steel posts around the Capitol Building is one of the largest (and most uniform) of its kind in the world.

New York City's smallest piece of private property.

A former waterfront market is now in the center of town due to some interesting Boston engineering.

This public park was the site of the largest civilian disaster of the Civil War.

The profile of one ill-fated deacon was emblazoned forever on this church window during the Halifax explosion.

One of England's most famous churches hides a pair of little known architectural treasures.

The sounds of the world's largest fully functioning pipe organ dazzle shoppers at a Philadelphia Macy's.

This elaborate towering structure was once famed for its revolutionary height.

The first American department store, and home to the largest operating musical instrument in the world.

Yo, Adrian!

A clone-tree in Washington Square Park sprung from seeds that went to the Moon and back.