The Grotto

The Grotto, on the rugged northern coast of Saipan, is one of the most spectacular natural sites in the Northern Marianas and a world-renowned diving destination. A large limestone cavern whose roof has partly collapsed, it holds a pool of astonishingly vivid, deep blue seawater, connected to the open ocean by a series of underwater tunnels and archways. Divers descend a long flight of stone steps to enter this cathedral-like chamber, then swim out through the tunnels into the sparkling sea beyond, amid shafts of sunlight, coral and marine life, an unforgettable experience regularly ranked among the finest cave dives on earth. Even for non-divers, peering down into the glowing blue pool from above is a striking sight.

The landscape

• The blue pool - the vivid deep-blue seawater cavern.
• The underwater tunnels - the passages to the open ocean.
• The light shafts - the sunlight streaming into the chamber.
• The dive experience - the world-class cave diving.

When to go

December to June, the drier season, brings the calmest, clearest conditions best for diving, avoiding the rougher, wetter months; the tropical climate is warm year-round. Calm seas are essential for safe diving through the tunnels.

Things to know

The Grotto is primarily a diving site, and its underwater tunnels and sometimes surging conditions make it best suited to experienced, guided divers rather than casual swimmers, while non-divers can only admire the blue pool from the steps above. As one of the most spectacular cave-dive sites in the world, a cathedral of vivid blue water and light, though, the Grotto is a genuinely extraordinary natural wonder.

Nearby

The northern beaches, cliffs and war memorials of Saipan lie nearby.