This daunting 1st century fortress was purportedly the site of one of the most dramatic revolts of the Jewish-Roman wars.

Gliwice Radio Tower, likely the tallest wooden structure in the world.

This underground church is topped with a 500-foot cross that is seen by many as a beacon of fascist hubris.

Commonly acknowledged as the only public monument to the Devil himself.

Madrid's romantically ornate crystal palace has been offering shelter to plants and art for over a century.

Abandoned for decades, trains still pass through the now-restored remains of one of Madrid's first metro stations.

An ancient Egyptian temple in the middle of Madrid, Spain.

Over two centuries old and counting, Madrid's massive botanical garden contains one of Europe's only desert environments.