Legend has it that President Grant’s frequent drinking in the lobby gave rise to the term “lobbyist.”

The unbelievably opulent home built for an infamous newspaperman.

What was once the largest NFL stadium.

The grand marble structure next to the White House is Andrew Carnegie's temple to Pan-American diplomacy.

Every drop of D.C. tap water flows through this old waterworks.

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

The bridge's highly-contested plaque (once again) honors Confederate President Jefferson Davis.

This Old Testament garden features 100 plants from biblical times.

Once the supplier for noteworthy projects like the National Cathedral, this old brickworks now lies abandoned.

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

Twenty-eight years after this local landmark was washed ashore by hurricane Hugo, it was washed away by hurricane Irma.

Once the most flame resistant building in the country, the South Carolina Historical Society building was almost burnt down in a fire.

The most accurate timepiece in the world.

This seemingly out-of-place gas station by the Watergate hotel was once described as the most expensive gas station in the world.

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

One critic described it as "middle Mussolini, early Ramses, and late Neiman-Marcus." Another called it an architectural "natural disaster."

An extensive collection of reliquaries containing the bones of saints housed in the largest Catholic church in Venice.

"Congress may voluntarily remain in session throughout the summer, in order that our Congressmen may be protected from the intolerable discomforts and dangers of the ordinary outdoor weather!”

This $3 million model train takes you through Chicago, Seattle, and the thousands of miles in between.

This fort down the Potomac from Washington, D.C. was once the only defensive fort protecting the capital.

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

Before Metro, Washington had a robust streetcar network—and you see the remains of this infrastructure if you know where to look.

Decades before the scandal, this staircase on the river was a literal "water gate."

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