Freeway Park

Freeway Park, officially known as Jim Ellis Freeway Park, is an urban park in Seattle, Washington, United States, connecting the city's downtown to the Washington State Convention Center and First Hill. The park sits atop a section of Interstate 5 and a large city-owned parking lot; 8th Avenue also bridges over the park. An unusual mixture of brutalist architecture and greenery, the 5.2-acre park, designed by Lawrence Halprin's office under the supervision of Angela Danadjieva, opened to the public on July 4, 1976, at a cost of $23.5 million.

Source: Wikipedia