The Persian Gulf-an over 2500-year old name,in Darius inscription it is mentioned as a sea which rises from Pars, Strabo, the Greek geologist (500 B.C.), and Ptolemy, the greatest astronomer and Geographer of second century called this sea as Persian gulf. The entering part of the Persian Gulf in the strait of Hormuz is 85 kilometers and the ending part of it is 320 kilometers. The widest part is 325 kilometers. The Persian Gulf is 226 square kilometers and its average depth is 35, which reaches to about 90 or 100 meters in some parts. Kish, Qeshm, Abo Mosa, Tonb-e-Bozorg, Tonb-e-Kochak, Khark, Lavan, and Hengam are important islands of Persian gulf. Iran has borders with Qatar, The United Arab Emirates, Saudi Arabia, Iraq, Kuwait and Bahrain through this gulf.