Giant acorn-shaped 19th century gazebo from which suburban Washingtonians gazed upon the original "silver" spring.

A lawn full of retired spacecraft on display at one of NASA's first research labs.

Once America's tallest structure, now a Baltimore landmark.

The whole world in one water tank.

George Washington's dentures and Queen Victoria's dental instruments are in the nation’s official museum of the dental profession.

This bug-eyed water wheel uses the power of the Sun to clean up Baltimore Harbor.

The longest escalator in the Western Hemisphere takes over three minutes to ride down.

Once home to seven different roller coasters, Glen Echo has undergone many transformations since its founding in 1891.

The shelves in the back of this thrift store are devoted to saving, not selling, retro tech.

This dig site outside D.C. is known for its exceptionally high density of baby dinosaur fossils and dinosaur eggs.

A priceless collection of the Nation's cryptologic history.

A local farm's collection of unusual structures from a now defunct storybook amusement park.

The land is home to swimming ponies and a legendary 18th-century treasure.

An astounding collection of medical specimens, including bits of President Lincoln.

The trials and tribulations of marking Poe's grave.

Once decrepit and slated for demolition, now one of the longest pedestrian bridges in the world.

This funicular railway rumbles along for a mile up the nearly vertical face of Chattanooga’s Lookout Mountain.

The last holdout of a pre-Civil War rebel who took the matter of slavery into his own hands.