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

With over 100 jam-packed rooms to explore plus elaborate tea services and events, the Mansion on O Street is a hidden treasure.

Thermal springs underneath the seabed provide the heat and bubbles for these beachside natural hot tubs.

Washington's iconic carousel has a nice piece of Civil Rights history.

A tribute to the beloved, kind-hearted "homeless mayor" of Silver Spring.

The longest escalator in the Western Hemisphere takes over three minutes to ride down.

Giant acorn-shaped 19th century gazebo from which suburban Washingtonians gazed upon the original "silver" spring.

This handsomely carved wooden church is more than 800 years old.

In downtown Oslo, a menacing and terrifying relief clings to a church wall.

New York City's only radical feminist independent bookstore.

This whimsical group of statues is a favorite of children who love to climb all over Lewis Carroll's beloved characters.

Historical figures from New York City's Catholic community reside in Midtown.

One of the oldest standing structures in Montgomery County, Maryland.

Near-constant high winds deform the trees on Spruce Knob, the highest point in West Virginia.

The design of this beautifully crafted building was inspired by Norwegian glaciers.

This floating sculpture of ice is a poignant reminder of nature's power.

A Viking-style brewpub named for a Norse sea giant, in the heart of fjord country.

One of the most breathtaking railways in Europe also takes one of the steepest climbs, from fjord to mountain plateau.

This inverted metropolis model is the artist's "revenge" for not being allowed to have a doll house as a kid.

Denmark’s never-ending bridge.

The feral felines of Roosevelt Island have a small army of allies and an abandoned hospital all to themselves.

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

Built in the 1850s, this church was of the first five churches constructed in Harper's Ferry.

This shale formation along the Appalachian Trail once inspired the third president of the United States.