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

One of the largest aviation events in the world brings half a million aircraft enthusiasts to Wisconsin each year.

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

This pre-Revolutionary War grist mill ground corn and flour for soldiers in seven American wars.

An eerie, decaying ghost town destined to fade into the forest.

The haunting "Hell House Altar" is one of the few remnants of an abandoned college that has been a magnet for local legends.

Once part of a dam servicing an early 19th century grist mill, the tucked-way falls are a tricky-to-find urban oasis.

The trials and tribulations of marking Poe’s grave.

Once America's tallest structure, now a Baltimore landmark.

The land is home to swimming ponies and a legendary 18th-century treasure.

The stone marker that Mason and Dixon placed at the eastern end of the famous north-south border they surveyed.

Ruins of a once-prized railroad station in New York.

Landmark dedicated to the plight of the American Indian in the 21st century.

Antiques and recycled art surround this cabin designed to resemble a 19th-century schoolhouse.

Check out the 125-pound chocolate reindeer in the back of this candy shop.

A serene plaza that commemorates one of the Granite State's most iconic figures.

The highest point in the state of New Hampshire, and while unlikely "the worst weather in the world," it sure seems that way to hikers.

Near the summit of Mount Washington, a stone monument remembers a life lost to one of the mountain's infamous storms.

A beautiful Gilded Age hotel in the White Mountains with surprising diplomatic history.

A unique collection of old miners' cave homes carved in to the hillside cliffs near Death Valley.

The second tallest railway trestle bridge in America.

Standing 191 feet tall and measuring more than 55 feet in circumference, this is the world's tallest spruce tree.

This large Sitka spruce that appears to be floating in mid-air, has defied logic for years.

A community gathering place that once housed half-ton tanks and the World's Fair.