Pisa Province extends from the alluvial plain of the Arno River, in western Tuscany, to the Ligurian Sea and has the shape of a gun upside down. It is bordered to the north by the Province of Lucca, to the east by the Metropolitan City of Florence and Province of Siena, to the south by Province of Grosseto, and to the west by the Province of Livorno and the Ligurian Sea. The province contains 39 comuni (municipalities). The most populous cities in the province as of 2013 are Pisa (86,494), Cascina (44,040), San Giuliano Terme (31,039), Pontedera (28,793), San Miniato (27,580), Ponsacco (15,503). The northern area is mountainous, containing the Apennine mountain range of Mount Pisano, adjacent to the extreme offshoot of the Apuan Alps, that separates the province of Pisa from Lucca. The highest point of Monte Pisano range and of the province is at Monte Serra (). The Pisan coast, extends for about , and includes the following locations: Calambrone, Tirrenia and Marina di Pisa in the Municipality of Pisa, a stretch of coast about , protected as a park and administered by the City of San Giuliano Terme; Vecchiano Marina, in the municipality of Vecchiano, is also located in the park. The area of Pisa is flat, but, a few miles further south, in the southern part of the province, is classic Tuscan landscape consisting of hills, forests and ancient villages. Of particular note in the south is the Val di Cecina, the valley of the Cecina River, and the ancient city of Volterra to the west. The southern area of the province is hilly, containing the peak of Monte Aia dei Diavoli (867m). Demography Statistics recorded since 1861 show that the population of the province has increased gradually, from 240,000 is the 1860s to c. 390,000 in the 1990s. Since the new millennium, it has increased by some 30,000 to over 420,000 today. As of 1 January 2014, the ten most populated municipalities were Pisa (88,627), Cascina (44,901), San Giuliano Terme (31,315), Pontedera (28,915), San Miniato (28,072), Ponsacco (15,609), Santa Croce sull'Arno (14,528), Castelfranco di Sotto (13,431), Santa Maria a Monte (13,197) and Casciana Terme Lari (12,536), Economy The Province of Pisa has a wide variety of companies and organisations in the public and private sectors. One of the main areas of production is leather and footwear, where some 800 enterprises employing about 10,000 workers manufacture