An 18th-century Spanish watchtower made entirely of seashell and concrete.

A tribute to Ponce de Leon's supposed quest for eternal youth.

A luxurious 1880s hotel with its fair share of Tiffany stained glass, Edison electricity, and of course, ghosts.

St. Augustine's record-setting narrow street was designed to protect against pirates.

The language and heritage of a nearly forgotten culture can still be explored in this Southern enclave.

On Hilton Head Island this bronze King of the Sea rules all things briny—and lets you know if you’re late for lunch.

At 135 years old and counting, this historic print shop is heaven for poster nerds and music buffs.

A psychological self-portrait in the form of a giant, segmented head.

This research center for rare prosimians is studying how they sleep to help prolong human life.

This rare triple-jurisdiction drawbridge passes through Virginia, Maryland, and Washington, D.C.

A sacred site for Native Americans surveyed by George Washington and owned by both King George III and Thomas Jefferson.

At Washington's Dulles Airport is a satellite museum (no pun intended) with three quarters of a million square feet of aircraft history.

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

This charming colonial alleyway is one of the oldest continuously used residential streets in the U.S.

An Irish Memorial commemorating those who perished due to potato blight.

Ant sculptures march up the side of what used to be an iconic spot in punk rock lore.

A museum dedicated to the strange and extravagant costumes and memorabilia of the mummers, a tradition older than Philadelphia itself.

The first American department store, and home to the largest operating musical instrument in the world.

This elaborate towering structure was once famed for its revolutionary height.

Dr Barnes' $25 billion private collection of art and arboretum.

A daily replay of the experiment that proved the rotation of the Earth.

America's most famous museum of medical oddities is home to the remains of Albert Einstein's brain.

An organ located deep within a cave, whose "pipes" are the geological features of the cave itself.

What looks like a simple quaint estate in rural Pennsylvania was in the 18th century home to a small monastic community.