This Pennsylvania cave holds evidence of the oldest known inhabitants of North America.

Color-coded signs direct drivers on a network of routes designed to avoid Pittsburgh traffic.

Sections of the iconic limestone columns have been left uncleaned as a reminder of the city's polluted past.

A tiny piece of the Moon is embedded in this stained glass masterpiece.

The sci-fi villain is a little-known inhabitant of the U.S. capital's largest cathedral.

One of many reminders of Tesla's scientific contributions overlooks the falls which inspired him.

The Pennsylvania landscape depicted by a quarter mile of mosaics made from used road signs.

Memorializing an American tragedy of massive proportions.

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.

A historic beacon built in the aftermath of the worst maritime disaster on the Great Lakes.

A take-out restaurant that only serves cuisine from countries with which the United States is in conflict.

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

Lyon, France is home to two remarkably preserved Roman theaters, one dating back to 15 BCE.

These mysterious ancient stone spheres were created by a civilization lost to time and are now mostly lawn ornaments.

The heroic sled dog of the 1925 serum run is preserved in taxidermy.

This spectacular public market has got meat, fish, vegetables, baked goods, and enough kielbasa for a lifetime.

Medical history museum featuring a lovely doctor's office from the 1800s.

The only Bahá'í house of worship in North America and one of only a handful worldwide.

A museum cafe showcases Native American dishes and indigenous ingredients from across the Western Hemisphere.

Largest Roman Catholic church in North America.

Home to items never before seen by the public.

The last remnants of Fort Pitt also hold the distinction of being the oldest structure west of the Allegheny Mountains.

The United States’s oldest funicular railway glides up and down a steep Pittsburgh street.