An echo chamber with a waterfall wrapped around its base at the Embassy of Canada in Washington, D.C.

Once a sewer culvert, this road tunnel now offers cyclists and pedestrians a subterranean stroll under the C&O Canal.

A striking memorial to the 21 lives lost in an explosion at the Washington Arsenal

Railroad officials in the early 1900s sought to spare travelers the sight of Roman soldiers’ private parts.

The word "Watergate" will forever be associated with the infamous scandal in 1972, but this fountain is famous in its own right.

A tribute to the pop culture icon overlooks this Washington D.C. intersection.

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

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.

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

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

A secret greenspace hides atop a Capitol parking garage.

Through the decades, Black music stars have performed at this historic hub for music and the arts.

An ear-piercing buzzer calls lawmakers to a vote with a series of long and short rings to form coded messages.

A line of blue paint marks the route of the inaugural parade.

An obscure federal monument honors the French diplomat who served as Ambassador to the U.S. during WWI.

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

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

Also known as the Founding Church of Scientology.

A hidden passageway now marks the site of an assassination attempt on Ronald Reagan that some say broke a 140-year-old curse.

One of the most influential presidents in U.S. history wanted only this plain, elegant monument as his lasting memorial.

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

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

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

The first memorial dedicated solely to the Black troops who fought for the Union.