Ninety feet off the valley floor is an ancient dwelling put under protection of the U.S. government by Teddy Roosevelt.

Medicinal spa created from the mineral-rich runoff of a geothermal power plant

One of Antoni Gaudí's most classic buildings is well-known for its "dragon-back" design.

The gorgeous library at Trinity College is home to remarkable treasures of Irish identity.

Hundreds of lucky felines haunt the ruins where Caesar was murdered.

A miniature rainforest is growing inside of a Midtown Manhattan office building.

Kings Cross Station pays tribute to its role in Britain's best-selling book series.

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

The only structure left with direct ties to the Salem witchcraft trials of 1692.

This 1920s Dutch barge is now a floating bookstore.

Elevated freight railway turned wildly successful urban park.

This iconic Parisian bookstore doubles as the "Tumbleweed Hotel" for traveling writers.

Eighty million natural history specimens call this gargantuan museum home.

This striking arch, one of the first architectural elements constructed in Prospect Park, was recently restored to its original glory.

A century-old magnolia tree is the only living landmark tree in New York City.

Now the site of a high school, this was almost the location of the largest cathedral in the US.

This beautiful Brooklyn monument over a crypt memorializes a grim and largely unknown story from the American Revolution.