Daredevil repair workers can worm their way out the access hatch, loop ropes over the apex and rappel down the monument.

A tiny monument to the unsuccessful attempt by Thomas Jefferson to place the prime meridian in Washington.

Architecture lovers won’t stop touching the National Gallery's 19.5 degree marble prow.

A much-maligned monument to teetotalism.

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

The most accurate timepiece in the world.

A celebrity from the late Cretaceous period.

A super-sized promotional trick that is now a D.C. landmark.

The oldest continuously operating fish market in the United States.

A Civil War fort in the middle of Washington, D.C. has been swallowed by a forest.

A painfully obvious spy house sits right across the street from the Russian Embassy.

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.

A muscular Art Deco monument represents the struggle between regulators and unbridled markets.

"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!”

A historic ruin just 20 feet away from a busy highway onramp.

The national park was once a plantation estate.

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

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

The sculpture's largest spire points directly toward the North Star.

This super-sized statue is the only public memorial to the deal that ended America's neutrality during World War II.

A sarcastic monument threatens to curse any "idiot" who dares remove it.

A morbid gateway to an Alaska town prides itself on the hunting history it represents.

Running under an entire mountain, the longest highway tunnel in North America is kept fresh using portal fans and jet fans.

This small city where almost everyone lives in the same building can only be reached via North America's longest tunnel.