Tripoli, or Tarabalus Al-Gharb (Tripoli of the West in Arabic), is the major city and de facto capital of Libya. The climate of Tripoli is Mediterranean with hot dry summers, cool winters and some modest rainfall. Weather can be variable, influenced by the Sahara Desert and the Mediterranean Sea which moderates daily temperature ranges. The old walled city of Tripoli, the Medina, is one of the classical sites of the Mediterranean. The basic street plan was laid down in the Roman period when the walls were constructed on the landward sides against attacks from the interior of Tripolitania. The high walls survived many invasions, each conqueror restoring the damage done. In the 8th century the Muslim ruler built a wall on the sea-facing side of the city. Three great gates gave access to the town, Bab Zanata on the west, Bab Hawara on the south east and Bab Al-Bahr in the north wall. The castle, Al-Saraya Al-Hamra, occupies a site known to be pre-Roman in the east quadrant of the old city and still dominates the skyline of Tripoli. Any tour of the old city should begin at the castle, entered from the land side near Suq Al-Mushir. It houses a library and a well-organized museum and has excellent views over the city from the walls. The Castle Museum is essentially concerned with the archaeology and ancient history of Libya. It covers the Phoenician, Greek and Roman periods well and has an expanding collection of materials on the Islamic period. The old city has several key elements worth visiting. The old city walls are still standing and can be climbed. The Harbour Monument stands at the gates of the old city on the edge of the former corniche road adjacent to the castle. There are a number of restored houses, consulates and a synagogue in the narrow streets of the old city. There are a number of interesting mosques including the Karamanli Mosque, the En-Naqah Mosque and the Gurgi Mosque both in the old town and adjacent to it. The best known of the Tripoli mosques is the Gurgi Mosque with its elegant architecture. It was built comparatively recently in 1833 by Yussef Gurgi. If the travellerGurgi Mosque is the one to choose. Modern Tripoli spilled out from the tight confines of the old city as early as the 18th century and possibly before that. The main commercial streets lie in the centre. Most lead off Green Square in front of the castle. All street names are in Arabic but Libyans will assist in giving directions. Walking around Tripoli centre is straight forward. For a tour of the modern city on foot begin in Green Square and travel West along Sharah Omar Mukhtar to see the private business district. wishes to view just one of Tripoli's mosques, the Turn round at the Tripoli Fair building and return to Green Square from which go due South down Sharah Mohammed Magarief towards the post office and former cathedral. From the post office square (Maidan Al-Jaza'er) either turn directly right to Sharah Tahiti and thence right again into one of the commercial thorough-fares with small Arab lock-up shops or go on past the post office towards the People's Palace and thence right to the harbor front and back towards the Green Square. This itinerary shows the best if the modern city.