This historic Pittsburgh tennis complex is a rare example of natural red clay courts.

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

America's first public mental health facility.

The largest clock face in the United States is twice the size of Big Ben and infinitely more ad-sponsored.

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

One of the oldest living oak trees in the Southeast.

This lush forest valley was once mined for lumber to the extent that it was once nicknamed "The Pennsylvania Desert."

"Dark Sky Park" is heaven on Earth for astronomers, one of the rare U.S. locations with no artificial light pollution.

The highest point in Tennessee, Clingmans Dome bears witness to the ravages of one type of insect.

The lost ruins of the forgotten ferry lie hidden beneath the silt.

A Saint Nicholas-themed ghost town in the Mojave desert.

All of the 20 occupied houses in this mostly abandoned town feature some curious display of junk art.

A Norwegian-born sculptor created these soaring guardian angels at the entrance to Hoover Dam.

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

In the parking lot of a fast food restaurant, a statue memorializing a prolific bull elephant.

The Grand Ole Opry's big voice came from a small home in rural Virginia where she was eventually buried.

Outsider art meets paleontology at this roadside reptile repository.

An eponymous directional signpost erected by the first president of the United States.

These massive concrete balls were used to mine gold in Virginia.

Giant busts of 42 U.S. presidents are sitting in a field in Virginia.

Affectionately known as "Lord Bot," this historic statue has a cult social media following and rightly claims to be “the most metal inhabitant of the Wren Yard.”

The site of the little-known Pennsylvania battle that sparked the Seven Years' War.

The highest point in Maryland is only accessible by hiking through another state.

This claimant to the title of "smallest church in the 48 states" doubles as an equally tiny, quasi-post office.