Obscure Freemasons still live in D.C.’s largest private residence.

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

The actual model from the original "Star Trek" series is now on display at the National Air and Space Museum.

The famous abolitionist’s preserved estate is one of Washington's finest monuments to its great Black citizens.

A Spiritualist house of worship where believers communicate with the dead in the spirit world.

When it opened during the final years of the embargo, all the drinks and cigars were free.

An Industrial Revolution-era public work that purified water using nothing but sand.

There’s a hidden military meme engraved on the World War II Memorial.

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

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

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

This grand gothic brewery has been pumping out suds for over a hundred years.