- The Denny Triangle is a neighborhood in Seattle, Washington, United States, that stretches north of Downtown Seattle to the grounds of Seattle Center. Its generally flat terrain was originally a steep hill, taken down as part of a mammoth construction project in the first decades of the 20th century known as the Denny Regrade, which is another name for the neighborhood on the regraded area. The name Denny Triangle, referring to the northeastern portion of this regrading project, is a term that has gained currency as this neighborhood has seen increasing development in the first decades of the 21st century.