An old volcano on Lanzarote, one of Spain’s Canary Islands, guards an unusual lagoon. The water’s verdant color, magnified by the black terrain it rests atop, makes it look as though it should be seeping from a cartoon villain’s lair or stewing with some sort of toxic sludge.

The Green Lagoon (also called Charco Verde and Charco de los Clicos) is formed by ocean water that becomes trapped in a crater on the beach that hugs the volcano’s western base. A combination of algae and sulfur give the oversized puddle its unexpectedly bright hue.

Its peculiar pigment makes for a beautiful sight. The green water, flanked by inky pebbles and ocher sediments, immediately captivates the eye. Nearby, the white-capped waves of the Atlantic Ocean lick the blackened beach beneath the volcano’s shadow.

You can walk right up to the lagoon’s edge for a lose look at its odd color or view it from the elevated vantage point. But, as it’s a protected area, swimming within it is not allowed (not that the water’s acid-green hue really invites swimmers, anyway).

The lagoon is located near Timanfaya National Park and Los Volcanes Natural Park, which both contain other impressive geologic features as well. Public access is allowed.