The Azure
Window is a Limestone natural arch on the Maltese
island of Gozo. It is situated near Dwejra Bay on the Inland Sea. The formation, which was created after two Limestone
Sea caves collapsed, is popular with scuba divers. The Azure Window is made of a Maltese limestone known as
Globigerina This is the second oldest rock found on the islands covering almost
70% of its area. Source