One of the largest-ever mental hospitals now sits abandoned, surrounded by 25,000 unmarked graves.

Ruins from the Parthenon and petrified wood line the interior of one of the world's most famous monuments.

One-of-a-kind museum inside the first Boeing 747-400 ever made.

Soldiers were buried next to Lee's house in the center of Arlington Cemetery to dissuade the general from reclaiming his property after the war.

Members of Congress have traveled between the buildings on Capitol Hill for a century hidden from tourists, press, and storm clouds.

An overlooked oasis of quiet on the grounds of Washington's monumental basilica.

This small hilltop church weaves the urban history of Washington, D.C. with the national history of the United States.

One of the three perfect vellum copies of this historic book known to exist is on display in a specially-designed case.

The design of this modernist church was revolutionary when it was constructed in 1942.

The snowbirds here are circus sideshow performers.

The first custom-designed building to showcase the works of Dale Chihuly is a wonderland of glass and light.

Nearly 200 prehistoric giants lurk among the trees at this theme park.

Built in 1981 in collaboration with Andy Warhol, this giant piece of pop art stands on the campus of Colorado State University.

Fascinating military history, awe-inspiring wildlife encounters, and endless outdoor adventures draw people to this sprawling park.

This old building has served as a bank, post office, library, and city hall.

A fascinating aviation museum where you can chat with the veterans who once flew the aircraft on display.

One of the oldest, tallest, and most haunted lighthouses in America.

The only Leonardo Da Vinci painting in the Western Hemisphere.

The pharmacy's retro ice cream mixer is one of the last of its kind.

The early 20th-century home features cutting-edge technology of the day, such as ammonia refrigeration and needle showers.

This saltwater swimming pool, which is the last of its kind in the United States, is slowly crumbling within sight of multiple high-end beachside hotels.

The spaceship-like theater, which is still in use, was one of the most popular exhibits at the 1964 New York World's Fair.

Icelandic settlement in Manitoba established in 1875.

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