Huge concrete structures designed as an early warning system for Britain to detect enemy aircraft.

An avant-garde artist is survived by his seaside garden.

Over thousands of years, this slot canyon was carved out of the bed of an ancient lake.

This well-preserved Cistercian Abbey in a romantic pastoral setting has inspired artists like the poet Wordsworth.

On this wooded path, a stained-glass window creates a spellbinding forest cathedral.

The mysterious, fantastical woodland inspiration for "The Lord of the Rings."

Quirky Welsh observatory unites art and science.

A Neolithic burial tomb connected with a colorful array of legends.

A rocky sea serpent hides caves, blowholes, and a spectacular natural bridge.

High Victorian fantasy created a fairytale castle out of a ruined fortress in Wales.

The enormous earthwork sculpture honors the ponies that lived and worked in the old colliery.

The painting on an aptly named street honors the 1980s slasher movie.

Recently restored menagerie of Victorian-era beasts.

The castle still holds traces of the abandoned Roman fort it was built atop.

Historic Hull Street was actually the first street with a proper name in the Boston area.

In 1958, an MIT fraternity pledge laid down on this bridge and instituted a new, unique unit of measurement.

Cliffs full of fossils at the portal to England's Jurassic Coast.

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

This bunker in northern France was built by Nazi German forces with the intention of launching up to 50 V2 rockets at London each day.

This medieval sanctuary's tree-framed door looks like a portal to a mythical realm.

A Reformation-era fiery figurehead once denoted this location as a print shop.

This home designed for chocolate magnate Antoni Amatller is an exquisite treasure-box of Catalan Modernism.

Also known as "Robin Hood's tree," this tree became a famed location along Hadrian's Wall before it was cut down in an act of vandalism.

This tree was grafted from the actual tree that led Isaac Newton to ponder the theory of gravity.