A massive, gleaming sea turtle with a rider atop its shell looks out over the horizon.

The world's tallest boat lift stands as a massive piece of industrial tourism.

Dummies recreate radiological discoveries from history.

Only museum in the world devoted to bookbinding and book arts holds a permanent collection representing five centuries.

One of the deepest indoor swimming pools in the world.

A diminutive plaque recalls the treetop sniper who almost killed Abe Lincoln.

Senators used to relax in the nearly forgotten marble tubs now hidden in the U.S. Capitol Building's basement.

A hoard of sky catalogs, astrophysical journals, even the works of Galileo and Copernicus.

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