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

Bacteria and algae give the salty water its bubblegum hue.

A stately palace has been converted into the world's largest cannabis museum.

Hundreds of stone stairs and a winding medieval bridge connect this haunting Spanish island to the mainland.

The largest Art Nouveau complex in the world is a Barcelona hospital with a 600-year-long history.

A lush indoor jungle fills this bustling Madrid transportation hub.

Bask in the 19th century grandeur of an eccentric Freemason millionaire's private gardens.

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

A beautiful but toxic fountain of mercury.

Astonishing rock formations dot the Brimham Moor landscape.

A modern English garden of eccentric beasts, follies, and oddities.

Old-fashioned knowledge and modern engineering create the world's only rotating boatlift.

Iceland's "Smoky Valley" is a beautiful river that is shrouded in a constant cover of steam clouds.

An Icelandic island full of diving birds and legend.

A trio of hidden hot tubs takes advantage of Iceland's natural geothermal vents.

Rising from the sea like a stone monster.

A modern artist's primitive stone faces and unique rock instrument join Iceland's terrain with its history.

A site of pagan worship which still attracts people looking for fairies.

The one-time stronghold of the noble Douglas family, now home to ghost sightings and nesting birds.

17th century streets hidden under Edinburgh were once a breeding ground for the black death.

A 18th century graveyard and its astonishing cortege of macabre iconography.

360° views of the city plus five floors of optical illusions and hands-on science.

The final resting place of soldiers' loyal canine companions.

One of the oldest scientific gardens in Britain, containing more than 13,302 plant species in its core collection.