Boise's climate is characterized as semi-arid with four distinct seasons. Boise is the headquarters for several major companies, such as URS Corp. Technology investment and the high-tech industry have become increasingly important to the city; the call center industry is also a major source of employment. Varney Airlines, founded by Walter Varney, was formed in Boise. The company is the root of present day United Airlines, which still serves the city at the newly renovated and upgraded Boise Airport. The Morrison-Knudsen Nature Center offers water features and wildlife experiences just east of downtown. Boise is also a regional hub for jazz and theater. The Boise Centre on the Grove hosts a variety of events. A number of recreational opportunities are available in Boise. World Center for Birds of Prey, Boise Towne Square Mall, Bogus Basin ski area, and the Zoo Boise are some of the city’s major attractions.