This Ukranian fortress is one of the best-preserved medieval castles in Europe.

This hidden fortress has been coined the "City of Ghosts."

This beautiful natural train tunnel is said to grant the wishes of visiting lovebirds.

This gorgeous reading room houses the oldest and largest art history library in the Netherlands.

Ninety feet off the valley floor is an ancient dwelling put under protection of the U.S. government by Teddy Roosevelt.

This secluded aqua waterfall in the Grand Canyon is the perfect swimming hole, and the Havasupai tribe's fiercely protected natural wonder.

Dramatic river bend surrounds a natural red-rocked pedestal.

Most-visited and most-photographed slot canyon in the American Southwest.

The first declared National Monument in the United States.

A waterfall 600 ft. inside a mountain, once the bane of gold miners, is now a spectacle of nature.

The highest point in South Dakota contains the ashes of Valentine McGillycuudy, the "Holy White Man."

This prehistoric sinkhole lured exclusively male mammoths to their death, much to the delight of science.

This replica stave church looks like a piece of Norway was simply plopped down in South Dakota.

The granddaddy of all tourist traps, built on ice water, jackalopes, and a giant dinosaur.

The world's largest mountain carving could fit all of Mount Rushmore inside it many times over.

Located within a historic park, the beacon is the oldest standing structure in Miami.

These remote Florida islands have a history of sea turtles and sunken treasures, and one of the world's largest coastal brick fortresses.

The first life claimed by this record-breaking peak wasn't lost to exposure or a fall but rather lightning.

This abandoned boat was left in place thanks to its rotting beauty.

The lighthouse central to the 1980s horror classic "The Fog" is, in fact, located in one of the foggiest areas of the Pacific Coast.

A volcanic tunnel illuminated by natural skylights offers a shaded respite from the desert sun.

California's own medieval Italian castle, authentic down to the 300-year-old iron maiden in the dungeon.

Canyon walls shrouded in ferns.

This strange seaside tower got its name from a wealthy eccentric who would hide coins among its stones.