A traveling postal dog covered 48 states and more than 140,000 miles, and he lives on as taxidermy, patched up with a rabbit's foot and a pig's ear.

An atomic bomb-proof strongbox protects the U.S. Constitution from terrorists and thieves.

Light bulbs, scrap wood, and tinfoil comprise this homemade throne of the gods.

The actual model from the original "Star Trek" series is now on display at the National Air and Space Museum.

Four bald cypress trees in Lafayette Square, across from the White House, mark the southern edge of a 100,000 year old cypress swamp.

The beloved statue at the National Academy of Sciences is oh so inviting to sit on.

A historic neighborhood church is reborn as a psychedelic arts collective.

A nostalgic bibliographic gem.

Largest Roman Catholic church in North America.

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

This imposing Masonic temple a mile from the White House was the first public library in Washington, D.C.

The most decorated dog of World War I is preserved in the Smithsonian.

The first purpose-built art gallery in the United States is once again open as a center of craft arts.

There's a 12-foot-tall replica of the Washington Monument hidden under a manhole nearby.

A hidden gem on the lawn of the U.S. Capitol Building designed by landscape architect Frederick Law Olmsted.

Long-abandoned trolley tunnels just a mile away from the White House are turning into an art space.

One of the dwarven trees dates back to 1625 and survived the Hiroshima bombing.

A monument in Washington D.C. marks the spot from which all other roads were supposed to stem.

A tiny piece of the Moon is embedded in this stained glass masterpiece.

Enormous piles of historically significant stones, dumped by Congress in a forest, and abandoned for 60 years.

The sci-fi villain is a little-known inhabitant of the U.S. capital's largest cathedral.

Home to items never before seen by the public.

The United States Capitol's former columns still stand.

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