The Blue Grotto is actually a number of sea caverns on the southern coast of Malta

Malta

Malta , officially known as the Republic of Malta , is a Southern European country consisting of an archipelago situated in the centre of the Mediterranean, south of Sicily, east of Tunisia and north of Libya, with Gibraltar to the west and Alexandria to the east.Malta covers just over in...

, west of the Wied iz-Żurrieq harbor near the village of Żurrieq

Zurrieq

Żurrieq is one of the oldest towns in Malta, and has a population of 12,000 inhabitants . Żurrieq is situated in the South West of Malta. The first documentation about it being a parish dates back to 1436 dedicated to St. Catherine of Alexandria. The island of Filfla is administratively a part of...

. It is located right across the small uninhabited islet of Filfla

Filfla

Filfla is a small, barren, uninhabited islet south of Malta, and is the most southerly point of the Maltese Archipelago. Filfoletta, a small rocky islet some 100 meters southwest of Filfla, has the southernmost point of Malta....

.

Every day from sunrise until about 1 pm a unique sight can be observed here. The location of the cave combined with the sunlight lead to the water mirroring showing numerous shades of blue. Several caverns mirror the brilliant phosphorescent

Phosphorescence

Phosphorescence is a specific type of photoluminescence related to fluorescence. Unlike fluorescence, a phosphorescent material does not immediately re-emit the radiation it absorbs. The slower time scales of the re-emission are associated with "forbidden" energy state transitions in quantum...

colours of the underwater flora; other caverns show a deep dark shade of blue.

The Blue Grotto is a popular destination for tourists on the island of Malta. It was also used for a scene of the 2004 film Troy, starring Brad Pitt.