The "Great Sewer" of ancient Rome is one of the oldest sewer systems in the world, and is still in use.

The incorrupt tongue of the patron saint of lost things is venerated in this basilica.

A dismembered holy head stares out from her beautiful reliquary at the St. Dominic Basilica.

An underground city of salt.

A church of bones, decorated with 40,000 human skeletons.

A dozen U.S. presidents have stayed at the historic resort, which was known as James Buchanan’s “Summer White House” from 1857-1861.

One of the world's oldest continually operating bookstores.

A beloved horticultural oasis on the grounds of a wealthy family's former estate.

This historic furnace was once used to produce cannonballs during the Civil War.

Memorializing an American tragedy of massive proportions.

Beautiful views of the surrounding hills and birds of prey can be found at this sanctuary.

The souvenir got the company’s founder out of a pretty pickle at the World’s Fair.

This extraordinary Depression-era expenditure was modeled after a postcard of a Mediterranean hotel.

A dramatic, 360-degree recreation of Pickett's Charge in the Civil War.

Steepest flood safety railway in the entire world.

A local prank turned town icon.

This shrine to McDonalds' most iconic sandwich holds a 14-foot tall burger.

The largest university building in the West is a gothic masterpiece containing dozens of theme rooms based on different countries.

There aren't too many operational funiculars around, but Pittsburgh has two!

The house that Frank Lloyd Wright "(shook) out of his sleeve at will" at the age of 86.

Yo, Adrian!

This might just be the TARDIS of bookstores.

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.

A restored Pittsburgh house of God has been converted to a marvelous house of suds.