Exact replica of the ancient monument, but much, much lighter.

An organ located deep within a cave, whose "pipes" are the geological features of the cave itself.

Hidden in plain sight on the Hudson River is an abandoned train station where nature has taken over.

The oldest active church in Pennsylvania is also the second oldest Swedish Church in the United States.

The final resting place of one of the United States's greatest poets.

Vacant Beaux-Arts buildings that serve as reminders of a beach town’s glory days.

The site of one of history's most indelible and horrific tragedies.

A random tree outside a Budapest hotel has become a DIY shrine to the late singer.

An elegant chandelier hangs over this ancient sewer chamber, now open for concerts and public tours.

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.

An early 20th-century bullring converted into a modern shopping center.

This collection of over 50 murals celebrates Brussels' rich history as the self-proclaimed home of the "comic strip."

A little sculpture with a large wardrobe.

One of the world's oldest working clocks is curiously missing the Zodiac sign of Libra.

This overgrown mountain village has been abandoned for nearly a century.

A trough of 700 strange bronze faces runs through a narrow alley in Ljubljana's old town.

Martin Bricelj Baraga's monolithic sculpture measures the blueness of the sky, and changes color to match it.

Dress up like a miner and take a slide into the disco-lit depths of this once foundational salt mine.

This modern castle sat empty for decades before a fire inspired its builders to complete its luxury halls.

America's post-nuclear-attack chambers of Congress.

These unusual rooms on wheels are holdovers from the 1960s.

The secret city built by the Manhattan Project.

This nine-story building can be played like an instrument.

This giant iron playfully pays tribute to an early 20th-century architectural trend.