If you can look past the nearby sewer pipes, this urban sinkhole grotto is a mini-paradise.

A disquieting Aztec sculpture displays hundreds of stone skulls representing the victims of human sacrifice.

This recently restored timepiece has stood all around Kansas City.

The first car-centric shopping plaza in the U.S. brought a little bit of Spain to downtown Kansas City.

This abandoned prison castle has become an imposing gallery of graffiti art.

Community bookshelf of 25-foot-tall book spines.

The only castle in North America to ever house European sovereigns.

Gilded heaven for philatelists and architecture freaks, still in full working order despite sitting atop tremulous ground.

Famously misunderstood wonder of the ancient world

An emerald-green grotto just a short trip from Austin.

The iconic boulevard is the perfect place to catch sight of a bicycling skeleton, a levitating Satan, or a chef with his head stuck in a pizza.

Vibrant street art created with mixed media.

A haunting tribute to pioneering photographer Clover Adams.

This imposing Masonic temple a mile from the White House was the first public library in Washington, D.C.

Once the largest windmill outside of Holland, with enormous 114 foot sails.

The key to turning shifting dunes into the green oasis of Golden Gate Park.

In all of the 29 years it was in operation, no prisoners ever escaped successfully... or so they claim.

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

Yo, Adrian!

This charming colonial alleyway is one of the oldest continuously used residential streets in the U.S.

World's first "penitentiary," meant to be humane, drove men insane.

A small park on Bourbon Street features life-size bronze statues of New Orleans musicians.

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

Construction of Barcelona's iconic (but controversial) church is expected to be completed in 2026—a century after the death of its architect.