The world’s first dedicated cloud observation platform.

This tidal island, a sacred site in early English Christianity, was the target of a notable Viking invasion.

This two-towered gateway is all that remains of the unluckiest pier in the world.

The tower was originally used as a chimney for the waste incinerator of St. John's Precinct and Market.

A remarkable feat of Victorian engineering across the Firth of Forth.

The world's shortest funicular ferries beachgoers a whopping 128 feet from clifftop to shore.

The ruins of a 15th-century castle that has seen its fair share of bitter feuds.

This hydraulic power system in London was, at one time, seen as a rival to electricity and the last of its kind to shut down.

Built in 1911, the Tees Transporter Bridge is one of only six transporter bridges still in operation.

400 million years of erosion shaped these fascinating seaside caves, which made an appearance on 'Game of Thrones.'

The ruins of a 12th-century seaside castle on the southwest coast of Scotland.

London's Victorian Tower of Babel.

Following years of secrecy, the hidden history of a World War II site is being brought to light.

The remains of one of Wales’ great medieval buildings, with a pub in the cellar.

This magnificent arch is all that remains of a former smelt mill.

This 20th-century replica of a 13th-century castle has itself fallen into ruin.

These formal gardens were designed to be admired from the vantage point of the castle.

This unique rock formation has become a popular walking trail.

The control tower at the historic weapons range is now available as a highly unusual vacation rental.

Once the last route taken by condemned prisoners.

Although it appears much older, this castle-like tower is actually a Georgian-era folly.

This impressive midden of scallop shells apparently all comes from a single fishing company.

A tumbling waterfall near a narrow passage that was used to herd cattle for hundreds of years.

The ruins of a 12th-century Cistercian monastery can be found alongside World War II tank traps and pillboxes.