Strange physical sensations and optical contradictions keep visitors coming back for more.

A larger-than-life version of the hat beloved by hunters, outdoorsmen, and Holden Caulfield.

The largest ski jump in the Western Hemisphere hasn't hosted skiers in decades.

These statues pay homage to the "green corridor" of parks and wetlands.

These grassy undulations on a stretch of University of Michigan campus aren't bad landscaping, they're art.

This lone tree and dramatic sandstone outcropping are so beloved by Michiganders they can be found on one of the state’s coins.

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

A derelict bit of infrastructure from the canal that once ran through D.C. is landlocked in the heart of the city.

This mysterious structure by the Washington Monument is a flood barrier designed to protect the White House against rising waters.

An overlooked memorial honoring the local Washington residents who died in World War I.

Those with a sharp eye can find the hidden image of a German Shepherd on the memorial's Mural Wall.

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

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

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

The innocent intentions of this monument are somewhat lost in the sculpture's muscled imagery.

Home to items never before seen by the public.

A spectacular tribute to statesman and philanthropist Andrew Mellon.

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

The walls of the iconic dome are hollow and have a secret stairway.

A little marble compass above George Washington's (empty) tomb in the Capitol marks where D.C.'s four quadrants intersect.

Rumor has it the uncarved lump behind the three famous suffragists is reserved for the first woman president.

This statue of the "father of television" stands prominently in the United States Capitol.

Washington D.C.'s most famous pianist, composer, and bandleader still tickles the ivories outside Howard Theater.

An amazing example of early-20th-century architecture, this church features marble transported from Utah.