Famously misunderstood wonder of the ancient world

The largest stone circle in the world has ended up bringing up more questions than it has answered.

Ancient man-made caves underneath small town Belgium.

Hiding the longest subterranean river known in the world.

This collection of solar timekeepers includes the world's first digital sundial.

A 14th-century fortified keep showcases the masterpieces of an ingenious 20th-century clockmaker.

Sculpture designed by Turkish artist and professor Mehmet Ali Uysal.

A magical and peaceful ruined Cistercian abbey in what is now southern Belgium.

An Italian crevasse filled with abandoned buildings gives visitors a look at the world without humans.

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

The world's most active stratovolcano is almost always erupting.

Geothermal waterfalls in Tuscany.

A sulfuric hellscape in southern Italy.

The crypts of Capuchin friars decorated with the bones of over 4,000 friars, including an entire "crypt of pelvises."

Thousands of well-dressed mummies below a monastery.

The vast, legendary catacombs hold secrets much stranger than stacked bones.

At the crypt of St. Mary of Eulogies and the Dead you are left alone to ponder mortality among piles of skulls.

An ossuary built in 1210 to collect bones from the Ospedale Maggiore of Milan.

Mysterious painted skulls in Moravia.

A church filled with the bones of hundreds of virgins martyrs—or so they say.

Retirement home for giant obsolete machines.

Between Neo-Pagans and Neo-Nazis, these strange rock formations have a curious cult following and a very strange history.

The resting place of 18th century German mummies.