This astonishingly geometric cave has inspired everyone from Jules Verne to Pink Floyd.

Overlooking a Scottish loch, this beautifully crumbling castle once inspired a poem by William Wordsworth.

The largest cave chamber in Britain—big enough to fit a whole cathedral inside.

This remarkably well-preserved Egyptian plinth is pretty well traveled for a giant piece of stone.

Five sultans and their families rest in eternal splendor, teeming with overlooked beauty and drama.

A stone copper was sculpted on the wall of the Carlisle Cathedral to honor a local hero.

Overlooked by many, the two famous Scottish warriors guard the main gate of Edinburgh Castle.

Ruined 11th century abbey built by King David I in Edinburgh, Scotland.

According to the Guanches, the aboriginal people of the Canary Islands, the king of evil lives inside this volcano.

Visit a surreal landscape so otherworldly NASA actually used it to train the Apollo 17 crew.

The chefs at El Diablo use heat generated by an active volcano to cook the food.

The iconic boulevard is the perfect place to catch sight of a bicycling skeleton, a levitating Satan, or a chef with his head stuck in a pizza.

Gaudí's famously flamboyant architectural style is on full display in this sprawling park and garden.

One of Antoni Gaudí's most classic buildings is well-known for its "dragon-back" design.

Construction of Barcelona's iconic (but controversial) church is expected to be completed in 2026—a century after the death of its architect.

One of the longest wooden benches in the world snakes around Geneva's Treille Promenade.

This ritzy Italian market is built around a statue of an unforgiven heretic who was burned for his belief in an endless universe.

The modern birthplace of Irish freedom.

A nun spent 16 years painting the stunning Celtic mural that covers the interior of this WWI memorial.

The somber sculptures commemorating Irish Famine on the river Liffey in Dublin.

The enchanting archway is the only surviving portal into Dublin's lost medieval wall.

Amidst the bustling streets of Dublin, there is a hushed garden that is dedicated to "All those who gave their lives in the cause of Irish Freedom."

The gorgeous library at Trinity College is home to remarkable treasures of Irish identity.

This abandoned Greek island was the last active leper colony in Europe.