Lago Martiánez
Because Puerto de la Cruz has uninviting black-sand beaches, the town commissioned Lanzarote artist César Manrique in 1965 to build Costa Martiánez, a forerunner of today's water parks. It's an immense—and immensely fun—public pool on the waterfront, with landscaped islands, bridges, and a volcano-like fountain that sprays sky-high. The complex also includes several smaller pools and a restaurant--nightclub.