Modern commuters still pass through this 2,000-year-old Roman archway.

This medieval castle overlooking the Elzbach river looks just like it did hundreds of years ago.

A collection of beautiful crystals shaped like freshly plucked roses.

The mysterious canine hides atop a drain pipe on the back of the building, some say as a sneaky shoutout to Yale.

The water swaps direction twice a day, whipping into a frenzy of whirlpools and rapids.

The marker offers a rare chance to be in four U.S. states at once, though there's some controversy over its geographic accuracy.

Rich red almandine gemstones are waiting inside the volcanic rock strewn across this eastern Nevada hillside.

An easily overlooked stretch of ornate window fronts and gaslight lamps that could be right from the pages of Dickens.

A historic covered bridge is but one example of an oddly prevalent American urban legend.

Some of the tallest ancient American ruins continue to inspire awe and curiosity.

America's oldest archaeological site or a muddled case of wishful thinking.

Everything you always wanted to know about borates is here.

"Polynesia on the Plains."

The home of the first American-born saint is one of the only curved buildings in New York.

Where the first "expert riders, willing to risk death daily" for the Pony Express were recruited.

A pair of large white marble lions guard this stretch of the Mojave Desert, and it is utterly mysterious how they got there.

This Old West eatery along America's Loneliest Road was originally a stop on the Pony Express.