The economy of San Diego is largely based on tourism, defense, and international trade. San Diego is home to the largest naval fleet in the world, and the city is a major hub for the defense industry. San Diego is also a major port of entry for goods entering the United States from Mexico and other countries. The city is home to a number of major companies, including Qualcomm, Sempra Energy, and Petco. San Diego is also a popular tourist destination, with attractions such as the San Diego Zoo, SeaWorld, and Balboa Park.