An impressive monument to Poland's independence.

One of only two places in the world where two rivers cross each other without the waters mixing.

The only natural lake in the world that drains into both the Atlantic and Pacific Oceans.

A beautiful geyser under environmental threat.

One of nature's most well-scheduled phenomenons resides in Wyoming's Yellowstone National Park.

A legal loophole makes it possible to get away with murder within this 50-square-mile section of Yellowstone.

The Pentagon sits on a former island that was in Virginia at low tide and D.C. at high tide.

An extensive, if one-sided, history of U.S. law enforcement's war on drugs.

The Pentagon is so large that it was planned like a city, complete with internal highway infrastructure.

Conveniently located within binocular range of a nuclear bunker, the "summer camp" area was a painfully obvious spy house.

Dr. Strangelove-esque tours reveal the inside a bunker once reserved for Stalin himself.

This Russian religious complex is a Frankenstein's chapel that includes influence from almost all the major faiths.

Stalin's secret bunker.

An auroral research program that superheats the ionosphere.

Thirty creepy ghosts now inhabit this decaying 14th-century church.

The deepest hole drilled in the name of science, where evidence of Precambrian life was found.

This disused church, left to the elements of the Arctic Circle's forests is open for exploration.

The walls of this medieval church are covered with perfectly preserved frescos, including a pristine example of the Dance of Death.

The church's remarkable frescoes incorporate Finnish artist Hugh Simberg's trademark themes of death and the supernatural.

Lucerne's central prison was converted into a tourist hotel with a bare minimum of changes.

The world's longest and deepest train tunnel.

The tallest outdoor elevator in Europe rockets passengers on a dizzyingly precarious ride to the top of a mountain.

The steepest classic funicular in the world glides along a dizzying incline.

Beneath Kraków Old Town's main square lies a hologram-filled medieval market vampire graveyard wonderland.