This historic hotel invented the chocolate brownie.

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

Renaissance hospital featuring a rotating door into which unwanted babies were dropped.

Venice's island of the dead.

The handiwork of a underdog clockmaker who solved an impossible problem for an Empire, and forever revolutionized seafaring.

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

The perfectly preserved underground rooms where Churchill plotted the war against Germany.

This stone gatehouse was once the entrance to a historic mountain resort, and it had a cameo in a cheesy cult horror movie.

Five sultans and their families rest in eternal splendor, teeming with overlooked beauty and drama.

Carvings in Turkey's Marble Road may have directed ancient Romans to a hidden brothel.

Michael Jackson got Bad and Crocodile Dundee walked on heads in this iconic Brooklyn subway station.

This picturesque Umbrian city has a subterranean side that has long remained hidden.

Thousands of narrow alleyways in an ancient medieval city make up what's believed to be the world's largest car-free urban zone.

The first and only carousel with a lineup entirely of insects.

A 98-room castle in the middle of Toronto that bankrupted a 19th century electricity multimillionaire.

The Atlantis of Cape Cod reemerges during the lowest of tides.

The tallest The Church of Jesus Christ of Latter-day Saints temple in the world soars above the Beltway.

This palatial botanical garden is home to one of the largest pipe organs ever installed in a private residence, and a piece of Wood's cycad.

Philadelphia boasts one of the best — and most often overlooked — traditional Japanese gardens in North America.

Equal parts record-breaking temple to consumerism and bizarre fun park, it's more than you think it is...

Iconic rock formations that allow for exploration during high or low tide.

On a former island, this old fortification once used to protect the Boston Area and started Edgar Allan Poe in his military career.

Berthed at the Charlestown Navy Yard in Boston, "Old Ironsides" is the oldest commissioned warship still afloat.

Two thousand artifacts from around the world collected by one woman who loved to travel.