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

The Byzantine, pre-Columbian, and medieval art at this stately mansion are some of the most under-appreciated collections in D.C.

A lovely aquatic park built by a one-armed Civil War veteran who made a fortune from lotuses.

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

Amid the sprawling Defense Intelligence Agency Headquarters is one of Washington's least accessible museums.

The last of nine massive kilns that produced many of the red bricks for buildings in Washington, D.C. and northern Virginia in the early 20th century.

Government testing at the asylum briefly explored using marijuana as a "truth serum" on Nazi prisoners of war.

The country's oldest continually-operated mini golf course lies hidden in plain sight, eclipsed by one of D.C.'s most popular tourist attractions.

The oldest continuously operating fish market in the United States.

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

This eye-catching sculpture of rural life seems a bit out of place at a suburban intersection in front of a car dealership.

A small brick parlor house and artist's studio located in the wilderness is surrounded by imposing suburban palaces.

A double agent hid information for the Soviet Union beneath this bridge for more than 20 years.

This sturdy, circular stronghold served as one of the forts that protected the Venetian Lagoon.

According to tradition this is the oldest church in Venice, but its actual age is a mystery.

This palatial spiral staircase was so unusual the name "snail" was given to the noble family who built it.

This deconsecrated church has seen many uses, from a tobacco storehouse to a cinema.

100 year tradition of fist fights, marked by marble footsteps.

The only museum with its curator—and her pets—buried inside.

Those who own or stay at this 500-year-old, allegedly cursed house often meet terrible fates.

In the past, Renaissance sex workers were encouraged to entice customers on this bridge.

A sinister pyramid in the Frari contains the heart of the famous neoclassical sculptor.

Go inside to really appreciate this 500-year-old technological masterpiece.

This bronze boar's snout has been rubbed to a golden sheen by visitors seeking good fortune.