A free-trade agreement with the United States took effect 1 January 2009, eliminated tariff barriers on all consumer and industrial products, and also provided strong protections for foreign businesses investing in Oman. Tourism, another source of Oman's revenue, is on the rise. A popular event is The Khareef Festival held in Salalah, Dhofar, which is 1,200 km from the capital city of Muscat, during the monsoon season (August) and is similar to Muscat Festival. During this latter event the mountains surrounding Salalah are popular with tourists as a result of the cool weather and lush greenery, rarely found anywhere else in Oman.