The city of Acre is a historic walled port city with continuous settlement since the Phoenician period. The city is strategically located in a natural harbor at the end of Haifa Bay on the Levantine Mediterranean coast. In addition to the coastal trade, it was an essential way-point on the coastal road of the region and on the road that cut inland through the valley of Jezreel. The initial settlement in the Early Bronze Age was deserted after a couple of centuries, but by the Middle Bronze Age a large city was established. Since then, it has been conquered and destroyed many times, surviving for centuries as nothing more than a large village. Today's city, with its citadel, mosques, khans and baths, is characteristic of a fortified Ottoman city of the 18th and 19th centuries. The Crusader city's remains, which date from 1104 to 1291, are almost completely intact, both on the ground above and below today's street level, and provide an extraordinary insight into the layout and structures of Jerusalem, the Crusader kingdom's capital in the Middle Ages. The old city of Acre has been designated as a World Heritage Site by the UNESCO. Major archaeological excavations have been underway since the 1990s, and there are efforts to protect ancient sites. Khan al-Umdan, the "Inn of the Columns," the largest of numerous Ottoman inns still standing in Acre, was scheduled for renovation in 2009. It was built by Jazzar Pasha at the end of the 18th century. It is located near the port. In 1906, on the occasion of the 25th anniversary of the reign of the Turkish Sultan Abdul Hamid II, a clock tower was added above the main entrance.