The Inland Sea is an inland lagoon in Dwejra, and is perhaps the archipelago's most spectacular natural landmark. The Inland Sea, and Dwejra Bay itself, were created millions of years ago when two limestone caves collapsed. The shallow inland lagoon is linked to the sea via a 100 metre cave in the cliff. On calm days, small fishing boats carry visitors out to sea through this tunnel, in order to see Fungus Rock and the Azure Window. The sea is used by fishermen and bathers, and is also a very popular diving spot. Overlooking the lagoon is the Chapel of St Anne, built in 1963 on the site of a much older church.