This underground oasis is one of North America’s most fascinating prehistoric places—and you can scuba dive in it.

One of the world’s largest and deepest freshwater springs, where mastodons once roamed.

Eat the ultimate iteration of Portugal's most beloved pastry.

The television series' iconic giant foot was borrowed from this classical painting.

The extra platform at Gloucester Road has been used for art displays for over 25 years.

A haunting statue called "Eternal Silence" has quite the reputation among visitors with active imaginations.

A strange and haunting monument of unknown origin in the historic Graceland Cemetery.

Each of these gorgeous, intricately decorated rooms is painstakingly crafted to the scale of 1 inch: 1 foot.

Thirteen trees representing the original thirteen colonies were planted with soil from historic Revolutionary battlefields.

A limestone grotto where daylight filters in from below and turns the water a beautiful turquoise. Also home to a small underwater nativity scene.

Used as an example in one of the first dictionary entries for "museum" in 1706.

The spot where three Protestant clergymen were burned at the stake during the reign of "Bloody Mary."

Once one of the largest rooms full of books in the world, this bookstore basement is still a treat for bibliophiles.

One of Europe's oldest libraries.

The only "Egyptian" pyramid in Europe and the legendary tomb of Remus.

The final resting place of the poets Shelley and Keats.

The Italian revolutionary's legendary wife is portrayed on horseback waving a gun and holding her child in this memorial on the Janiculum.

Historic fortifications form the boundary of Vatican City, but it’s not entirely surrounded by walls.

Breathtaking and huge 430 year old maps of Italy.

This ritzy Italian market is built around a statue of an unforgiven heretic who was burned for his belief in an endless universe.

Hundreds of lucky felines haunt the ruins where Caesar was murdered.

Brass cobblestones mark the places where individual Holocaust victims were taken from their homes.