The coastline of Manchuria is extremely short, consisting of about 690 miles or about one-eighth of the total boundary of the country. It extends from the mouth of the Yalu River to Shanhaikuan where the Great Wall joins the sea. The most important of the harbors is Ta-lien (Dairen) which is located on the east side of the Liaotung Peninsula. The harbor is protected on three sides by land, opening to the east. It is 36 feet deep at the entrance, with a minimum of 23 feet at low tide at the wharves. Lüshun (Port Arthur) is a land locked harbor situated at the southern extremity of the Liaotung peninsula, about 20 miles southwest of Ta-lien. This is the only port in Manchuria which is ice-free throughout the year.