Seattle is the most populous city in the northwestern United States. Seattle's current official nickname is the Emerald City, the result of a contest held in the early 1980s; the reference is to the lush evergreen trees in the surrounding area. Seattle is also referred to informally as the Gateway to Alaska, Rain City, and Jet City. The Space Needle, is Seattle's most recognizable landmark. Other notable Seattle landmarks include Pike Place Market, the Fremont Troll, the Experience Music Project (at Seattle Center), and the Seattle Central Library. The city is the home of Microsoft and many other high-tech businesses. Seattle has been a regional center for the performing arts for many years. The century-old Seattle Symphony Orchestra is among the world's most recorded and performs primarily at Benaroya Hall. The city also boasts lauded summer and winter chamber music festivals organized by the Seattle Chamber Music Society.