The macabre collection of Jacques Sirgent, an expert scholar on the undead and all of their trappings.

The vast, legendary catacombs hold secrets much stranger than stacked bones.

This whimsical castle of grottoes was the labor of love of a French postman, and one of the greatest achievements of outsider architecture.

These quaint French houses dangle precariously over a precipice.

This stunning natural double arch, the largest in the Alps, went undiscovered until 2005.

One of the four sanctuaries of Rieti's Holy Valley was the site of the first living nativity scene.

A mountain cave is the site of archaeological findings and Paleolithic rock art.

The last of Philadelphia's wood-paved streets is now a landmark of terrible engineering.

This tiny cottage surrounded by railroads is the oldest surviving structure in Fairmount Park.

This sculpture of a fisherman spent six years at the bottom of the Schuylkill River.

A legendary boxing venue and ring featured in Rocky V.

Alexander Hamilton’s creation caused quite a bit of controversy.

Hidden behind West Philadelphia rowhomes is a haven for migratory and local bird species both ordinary and rare.

The world's third-largest crystal sphere has sat in the Penn Museum since 1927 with the exception of one outlandish theft.

South Philadelphia is home to Keith Haring's only surviving in situ collaborative public mural.

A tiny, unmarked beer and whiskey bar above an Ethiopian restaurant in West Philly fails to conceal live bluegrass.

A tour de force of a fountain, memorializing a man who loved fountains more than anything else.

The body of St. John Neumann and his collection of hundreds of relics, on display in a Philly church.

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

This Philly landmark has a giant butterfly pavilion, three floors of insect displays, and withstood a $40,000 heist.

Current docking place of the SS United States, the fastest transatlantic ocean liner.

Erected in 1697 this Philadelphia bridge is the oldest surviving roadway bridge and perhaps the oldest stone bridge in the United States.

The abandoned coal loading dock is a canvas for unsanctioned art.

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