A former major munitions plant that has been converted into a sprawling art space.

This twice-relocated "Usonian" home is among the smallest built by master architect Frank Lloyd Wright.

This brick-lined pedestrian walkway was once a railway tunnel used during the Civil War.

The tomb was guarded by soldiers from both sides of the war, and some left their initials carved in the brick.

This colonial tavern played host to George Washington, Thomas Jefferson, and other famous early Americans.

This stately building in Alexandria, Virginia was built by Freemasons to honor one of their most famous members.

America's first federal monument.

The graveyard holding the remains of George Washington's slaves was forgotten for nearly 200 years.

The only place for a truly presidential dram.

This grave marks the passing of a historic Jane Doe whose identity remains a mystery to this day.

The narrowest house in America is seven feet of pure spite.

An original apothecary from 1792.

This beach pool offers a spectacle of crashing waves, blue hues, and a historical lighthouse.

This colorful gate stands as an entrance to the walled city of Old San Juan.

Archaeological sites and great food inside the island's largest mangrove forest.

An unnatural lake in a naturally beautiful setting.

The crumbling remnants of this 19th-century quarantine hospital hint at the touristy island's darker past.

This small fort played a huge role defending Puerto Rico’s capital city.

The abandoned remains of this once-thriving hotel looms over the city, awaiting an uncertain future.

Legend tells how a Spanish soldier disappeared from this isolated sentry box without a trace.

A magnificent waterfall nestled in the heart of the El Yunque National Forest.

This bleach-white graveyard overlooking the ocean is accessed through a tunnel.

The world's second largest single-dish radio telescope, once used to contact E.T.

This chapel on a cliff is renowned for its healing powers and was founded on the site of a supposed divine intervention.