This picturesque view of the Scottish Borders was beloved by Sir Walter Scott.

One of Scotland's most important modern structures, it just made the '100 Most Endangered Sites' list.

The stately remains of Llywelyn the Great's mighty fortress.

A remarkably well preserved tower dating all the way back to the Iron Age.

These stark white cliffs were spat up by the sea and are slowly being retaken by it.

This Gothic Revival castle used as a shooting location for "The Secret Garden" and other films.

The gutted remains of this Estonian mansion are a monument to a tragic love.

An empty relic of the Moscow Olympics crumbles away in Estonia's capital.

Man-made mineral caves house massive bat colony.

This disappearing geyser has been attributed to witchcraft, but really it's all about rainfall.

Mysterious craters may have been home to an ancient cult.

"There's nothing there," and other lies the KGB told us.

The ruins of an Estonian prison are drowning in the quarry lake where the convicts were once forced to work.

Besieged by war, this castle ruin has crumbled into a peaceful picnic spot.

At high tide this strange footbridge appears to have no purpose whatsoever.

Three bridges straddle a stream, one stacked upon the other.

This haunting stone chasm is a hotbed of mossy rock and English legend.

This crumbling folly looks like an enchanted left over from Middle Earth.

A hermit's tiny cell built into the cliffside that saved him in South Pembrokeshire.

This remote island village was in danger of depopulating completely until a tunnel was built to connect it to the rest of the world .

This isolated island is often capped by its own fluffy cloud.

This isolated structure beckons adventurers with sublime views of the Faroe Islands.

The narrow passages will challenge even the bravest driver.

Historic slum of Tartu.