This controversial Irish show cave is home to a massive formation known as the Great Stalactite.

A moody and picturesque riverside ruin overgrown with vegetation.

The oldest inn in Kilkenny was established by the first convicted witch in Ireland.

Local legend says the remains of Father Christmas lie within the medieval grounds.

One of Ireland's most infamous prisons for rebels including men, women and children.

Seemingly grown on some other world, these New Mexico rock formations look like a disused science fiction set.

A massive tribute to this small county's top agricultural product.

This shack nestled in a 120-acre forest of maple trees in Mont-Rigaud is a wonderland of sugary syrup.

The record holder for the world’s largest peach.

Ninety years of Sydney buses under one roof.

The abandoned remains of a once popular zoo, and the grave of the last known Tasmanian Tiger.

One of Catholicism's four major basilicas has a series of papal portraits that are said to predict the end of the world.

A treasure trove of Renaissance-era funerary art in a Roman church built on top of Nero's grave.

The "Greatest Sewer" of ancient Rome is one of the oldest sewer systems in the world, and is still in use.

A mysterious chasm in the heart of the ancient Roman Forum, the Lacus Curtius was once believed to be a gateway to hell.

Architectural monsters are devouring this palace's every door and window.

The famous boat that once ferried Bogart and Hepburn still floats in Key Largo after being abandoned for years.

This private skyway is filled with art and was expanded explicitly so that Hitler could appreciate a river.

A Nesting Doll of Churches.

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

Go inside to really appreciate this 500-year-old technological masterpiece.

The sign that drew attention to a young boy's cucumber stand is now the name of his fruit superstore.

An abandoned town is hidden in Great Smoky Mountains National Park.

Still standing despite its considerable slant, this tilted lighthouse has become a local symbol of resilience.