South Lake Union (sometimes SLU) is a neighborhood in Seattle, Washington, so named because it is at the south tip of Lake Union. The official boundaries of the City of Seattle Urban Center are Denny Way on the south, beyond which is Denny Triangle; Interstate 5 on the east, beyond which is Capitol Hill; Aurora Avenue N. (State Route 99) on the west, beyond which is Lower Queen Anne; and Galer Street, Lake Union, and E. Newton Place on the north, beyond which are Westlake and Eastlake., but like most Seattle neighborhoods, its precise boundaries are indeterminate. In particular Cornish College of the Arts and Vulcan Inc. properties such as 2200 and 2201 Westlake are officially in Denny Triangle for city planning and zoning purposes but often referred to as South Lake Union. The portion of South Lake Union east of Fairview Avenue N. is historically known as Cascade, Historic structures continue to stand in Cascade Neighborhood today. Its main thoroughfares are Valley and Mercer Streets (east- and westbound) and Dexter, 9th, Westlake, and Fairview Avenues N. and Eastlake Avenue E. (north- and southbound). The city is currently addressing transportation issues by changing Mercer Street into a two-way, six-lane, tree-lined boulevard. Valley Street will become a two-way, pedestrian friendly road. - source: Wikipedia