Siwa is famous for therapeutic tourism, as its sands contain natural elements suitable for alternative medicine. Safari trips using four-wheel-drive vehicles are also popular among visitors to the oasis. Some statistics indicate that Siwa receives around 30,000 tourists annually, both Egyptians and foreigners. Several international and Arab websites have ranked it among the nine most isolated places on Earth. The architecture in Siwa is distinctive, with traditional houses built from kershef stone—a mixture of salt, fine sand, and clay—and doors and windows made from olive and palm wood. Embroidery arts and handmade pottery are among the most notable traditional crafts of the oasis, including tajine plates and desert cooking pots with their traditional conical shape and decorative designs. Siwa residents celebrate a special festival, the Harvest Festival, which takes place on the full moon in October each year.