A nearly unconquerable island-fort in the Indian Ocean.

A former bastion of Rajput chivalry, this massive hill fort is the site of legend and tragedy.

This abandoned fort is said to be the most haunted place in India, so much so that entry is prohibited after sunset.

This otherworldly palace-mausoleum complex is the stuff eternal dreams are made of.

The remains of what was, not so long ago, the world's largest city.

A centuries-old fortress city lies in ruin.

A lake with hundreds of ancient skeletons surrounding it. The surprise is what killed them.

What was once an underground Nazi city is now Europe's largest bat reserve.

Deep in a Polish forest, this collection of Iron Age megaliths still holds onto many of its ancient secrets.

Crosses of all shapes, sizes and colors litter the mountain, the site of a huge yearly Orthodox pilgrimage.

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.

This man-made mound monument was built out of soil from all across the Polish empire.