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

Decades before the scandal, this staircase on the river was a literal "water gate."

D.C.'s first central library was born out of a chance encounter with the philanthropist whose name it bears.

The most accurate timepiece in the world.

Art deco landmark on the outskirts of Washington, D.C.

The privately owned cemetery that holds room for Washington's finest when they step down from life.

A traveling postal dog covered 48 states and more than 140,000 miles, and he lives on as taxidermy, patched up with a rabbit's foot and a pig's ear.

The only Civil War battle in Washington D.C. took place near this highest natural point in the city.

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

The beloved statue at the National Academy of Sciences is oh so inviting to sit on.

Fittingly, America's museum of architecture is itself a magnificently designed old building.

Four bald cypress trees in Lafayette Square, across from the White House, mark the southern edge of a 100,000 year old cypress swamp.

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

A derelict bit of transportation infrastructure hidden in the woods.

This imposing Masonic temple a mile from the White House was the first public library in Washington, D.C.

Largest Roman Catholic church in North America.

The first purpose-built art gallery in the United States is once again open as a center of craft arts.

The sci-fi villain is a little-known inhabitant of the U.S. capital's largest cathedral.

The site of the climactic scene from the classic horror film is now a historic landmark.

This shop and studio is dedicated to the art of the book, from letterpress to bookbinding.

The grand, column-fronted, sculpture-adorned home of the ambitious digital library.

Relics of the 1894 Midwinter Exposition continue to delight visitors today.

An elaborate gift from Claus Spreckels is now a piece of San Francisco history.

Carnivorous plants, medieval aphrodisiacs, and the largest original wood structure glass conservatory in the western hemisphere.