This Nazi ruin was the site where Hitler was almost blown up by a suitcase bomb.

The former Nazi concentration camp stands as a museum to remember this dark chapter in European history.

This Polish cave has housed a dragon, a brothel, and an enduring legend.

Real bones which are said to have belonged to a Polish dragon.

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

Countless stories attempt to explain Poland's mysterious J-shaped trees.

The walls and ceiling of this Polish church are decorated with thousands of skulls, with another 21,000 skeletons just below.

An ancient system of freshwater caves filled with animal bones, including that of species long-extinct.

The winter home of millions of migrating monarch butterflies.

A uniquely robust and historic look at Mexico's omnipresent dance with Death.

A magical sinkhole on the Yucatán Peninsula is adorned with mini waterfalls and hanging vines.

High atop a Mexican rainforest mountain, this ancient pyramid once drew pilgrims countries away.

A church dedicated to the Mexican skeleton saint.

66,000 pieces of art, donated by one of the world's richest men.

Extraordinary sculpture garden created by an eccentric English poet.

Part bookstore, part café, and part forest.

Frida Kahlo's childhood home, now a museum of her life and works.

An Aztec snake god has taken the material form of an apartment complex.

These azure waters were thought to lead to the Mayan Underworld.

Infamous marsh filled with toxic waste, World War II-era London rubble, and dead mobsters galore.

A bronze plaque at an intersection in Hoboken marks the place where the game of baseball first took shape.

These unassuming lighthouses have seen the first reading of the Pledge of Allegiance, the first wireless transmission, and more than one mystery.

A whimsical monument deep in this park commemorates the groups that helped build it.

A simple plaque remembers an act of WWI terrorism that obliterated an island and forever scarred the Statue of Liberty.