A railroad tunnel that, upon its completion, was considered one of the engineering marvels of the modern world.

The flower-shaped temple in Virginia aims to transcend the boundaries of the world’s religions.

This museum devoted to the gothic author holds such interesting ephemera as his socks and walking stick.

A 300-yard long natural tunnel runs through a ridge deep in the Appalachian Mountains.

This maze-like slot canyon is a unique gem within an already fascinating geological area.

The remains of a failed attempt at medieval nerdery are hidden deep in the woods of Virginia.

Giant busts of 42 U.S. presidents are sitting in a field in Virginia.

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.

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

A historic estate packed with George Washington's heirlooms, and its own nuclear bunker.

A three-story tower of books about Abraham Lincoln is one of the more unusual monuments to the president.

A monument in Washington D.C. marks the spot from which all other roads were supposed to stem.

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

A wondrous old library overlooking the nation's capital.

Enormous piles of historically significant stones, dumped by Congress in a forest, and abandoned for 60 years.

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

With over 100 jam-packed rooms to explore plus elaborate tea services and events, the Mansion on O Street is a hidden treasure.

A collection of Witchcraft artifacts and occult paraphernalia started by the leader of the Long Island Coven.

The angel of death appears to weep black tears at this grave marker.

Take a drunken tour inside the world's largest known geode.

Specimens collected by the author of "Lolita" and self-taught lepidopterist are exhibited in his childhood home.

The oldest museum in Russia is home to a fascinating collection of nearly two million anthropological artifacts and anatomical curiosities.

Walrus skulls and narwhal bones were found here while excavating a 900-year old church.