Nittany Mountain is part of Pennsylvania's geologic ridge-and-valley province of the Appalachian Mountains. It is (approximately) the geographic center of Pennsylvania, and as a result, Penn State University was founded in State College. Two major sections in State College include the Downtown Improvement District and University Park. Some significant neighborhoods include Highlands, Orchard Park, West End, College Heights, Holmes Foster, South State College, Tusseyview, Greentree, Nittany Hills and Penfield, and Vallamont. Four of these neighborhoods, Orchard Park, Greentree, Tusseyview, and South State College, are included as one area called "Suburban" State College under the National Citizen's Survey. Downtown State College, also known as the Downtown Improvement District is the commercial and cultural center of the Borough. The area receives approximately 1.5 to 2 and boasts major festivals such as the Central Pennsylvania Festival for the Arts. Downtown State College boasts a population of around 4,417 people. State College is one of the densest cities of its population in the United States, primarily aided by the presence of numerous high rises downtown along Beaver and College Avenues. The 2010s saw a construction boom downtown, with several mixed-use towers being developed, including the Rise, Metropolitan, Fraser Centre, Here at State College (a 15-floor tower on Garner Street), among other projects. Unlike most older towers, many of the newer buildings are mixed-use, with retail on the ground floor, offices on the next couple floors up, and apartments on the top floors. This high rise building boom has drawn debate in the local area. Some residents see it as a boon to increase foot traffic downtown and reduce congestion on the arterial roads leading into the town. Others, however, are skeptical of the developments as they replace historical buildings in the area, losing some of the borough's character. University Park is the largest Penn State campus and the postal address for the University. Notable sites include Old Main, a landmark of the Farmers' High School Historic District, Rec Hall, the Nittany Lion Shrine, the Palmer Museum of Art, Penn State Creamery, Beaver Stadium, and the Bryce Jordan Center, the latter two being on the College Township half of University Park. From 1909 to 1932 annexation for the Highlands took place. The area was acclaimed for their plots of land in proximity to the post office. Twenty mansions were built between 1925 to 1933 to attract fraternities while smaller houses were also constructed. The neighborhood terminated around Irvin Avenue, but after World War 2 expansion was necessary to accommodate for returning soldiers.