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

Enjoy a slice while browsing the world's largest collection of pizza memorabilia.

Huge masonic hall in Philadelphia with lavishly themed rooms.

One artist's love letter to his city and its citizens plays out across dozens of bright murals painted on the sides of decrepit buildings.

The oldest surviving botanic garden in the United States.

This little-known collection holds everything from "Dracula" notes, to the manuscript of "Ulysses," to the forged works of Shakespeare.

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

Mural made of 100,000 pieces of hand blown glass, and until recently, the largest glass mural in the US.

A rare view of a preserved Victorian science museum.

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

A layered tribute to the work of mosaicist Isaiah Zagar.

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

World's first "penitentiary," meant to be humane, drove men insane.

A still functioning vaudeville carousel that has operated for over a century boasts a colorful menagerie and past.

The giant pair of sexy legs sticking out the window of this costume store have become its main draw.

An overlooked and unassuming engineering marvel.

In all of the 29 years it was in operation, no prisoners ever escaped successfully... or so they claim.

The highest point in North Carolina and the United States east of the Mississippi River, Mount Mitchell is named after argumentative explorer Elisha Mitchell.

An enormous, inside-out glass globe built in 1935.

This valley of hot springs and boiling mud pots is home to the record-holding "Geysir," which originated the English word.

If a glacial river suddenly diving into a sheer chasm via a dramatic, multi-stage waterfall isn't peak Iceland, it's certainly close.

This natural Icelandic fissure allows divers to swim right between two volatile tectonic plates.

This tiny museum's sizable collection is jammed into a former underground public toilet.

One of the tallest buildings in Iceland, and perhaps, the most visually impressive.