A giant hilltop cross marks the location of a sanctuary with stunning views of Acapulco.

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

The tomb was guarded by soldiers from both sides of the war, and some left their initials carved in the brick.

The graveyard holding the remains of George Washington's slaves was forgotten for nearly 200 years.

Over two centuries old and counting, Madrid's massive botanical garden contains one of Europe's only desert environments.

A cavernous three-story, 43,800-square-foot basement that was forgotten about for 60 years.

The romance of early commercial flight still fills this Art Deco destination.

This isn't your average roadway—it's actually a National Park and a transportation pioneer.

The 72-foot giant escaped confinement in a large patch of mulch only to be reburied in the sandy shores of the Potomac River.

A massive Montreal stadium that has seen nothing but trouble since its inception.

A contemporary fresco movement illustrates the region's rich history.

This lovely, if imposing, piece of Canadian gothic is possibly the most photographed hotel in the world.

A grand Gothic Revival basilica with stained glass depictions of Montreal's religious history has only one soul resting in its crypt.

Designed by Buckminster Fuller, this relic of the 67 Expo survived fire and ice.

A celebrity from the late Cretaceous period.

A double agent hid information for the Soviet Union beneath this bridge for more than 20 years.

Look closely and you’ll notice that the color changes a third of the way up the tower.

The oldest continuously operating fish market in the United States.

This unique historical monument features large concrete spheres designed to resemble fallen stars.

At 207 feet, one of the world's longest continuous escalators.

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

The little-known, 300-year history of the area includes former lives as a bustling tobacco port, parking lot, and industrial dump.

America's Most Wanted's set resides in this tribute to the history of crime and punishment.

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.