The Egadi Islands consist of three main islands, Favignana, Levanzo and Marettimo and two islets, Formica and Maraone. The province of Trapani has a number of rivers but most are not of notable size or importance, except for the Belice on the border of the province, and the Birgi, with a length of about 40 km. Other rivers include the torrential Modione, Mazaro, the Fiume, the Salemi and the Sossius, the latter of which flows into the Mediterranean Sea at the resort of Berbaro. Natural lakes include the Gorghi Tondi and Preola, in the comune of Mazara del Vallo, and the Lago di Venere in Pantelleria. There are also three man-made lakes, Lago Rubino, created by a dam across the Cuddia River, which is part of the catchment area of the Birgi, at Lago Trinità in Castelvetrano, and the lake of the same name at the resort of Paceco. However, there is also a coastal lagoon, the Stagnone Lagoon, within a 2000 hectare reserve on the stretch of coast between Punta Alga and Cape San Teodoro, near Marsala, in an area which was once an important naval base and commercial for the Phoenicians. The waters are shallow and very salty, with marshland. The lagoon consists of four islands: Isola Longa Santa Maria, San Pantaleo and Schola.