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

This quarter-mile tunnel under the Bluff in Pittsburgh bends at a 45-degree angle.

A model of a dinosaur that was named for Andrew Carnegie stands outside the museum that also bears his name.

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

Lines from a walking song are etched into a rock in Natural Bridge State Park.

A sacred site for Native Americans surveyed by George Washington and owned by both King George III and Thomas Jefferson.

Home of a 28-foot tall stalagmite known as the War Club.

Step into the courtroom to learn details of the only case in history where ghostly testimony led to a murderer's conviction.

This former fire tower is now a rustic observatory that offers amazing views of eagles, hawks, and the Appalachian Mountains.

Just your average Marie Antoinette–themed speakeasy in an abandoned 19th-century subway tunnel.