This picturesque medieval monastery guards a small trove of historic treasures.

Longest fortress system anywhere in Europe.

This crucial gathering spot along the "hippie trail" still displays old notes between traveling beatniks and backpackers.

Legend says if you stick your thumb in the hole and it gets wet your wish will be granted.

A marvel of Byzantine engineering under the streets of Istanbul.

Known as the most dangerous bridge in the world, the Hussaini Hanging Bridge is only one of many precarious rope bridges in Northern Pakistan.

This dazzlingly turquoise mountain lake was created in the wake of a natural disaster.

Tibetan-influenced mountain fortress in Northern Pakistan.

This grand Pakistani mausoleum can only be accessed via an almost 1,000 foot long alleyway.

These stairs were built to accommodate royals mounted on elephants.

A 17th-century mosque that was used for war more than worship.

Space-age minarets towering over Islamabad.

A naturally beautiful, seemingly bottomless deep blue spring.

Hundreds of thousands of concrete bunkers crowd Albania long after the fall of Communism.

A medieval bridge stretches over a sulfur-rich river that leads to year-round natural hot springs.

This fortress dates back to the 6th century and is also the site of a controversial abandoned restoration project.

The deepest underground city in Turkey was designed to protect 20,000 people behind massive stone doors.