The Seattle Central Library is the flagship library of the Seattle Public Library system. The 11-story glass and steel building in downtown Seattle, Washington was opened to the public on May 23, 2004. Rem Koolhaas and Joshua Prince-Ramus of OMA/LMN were the principal architects, and Magnusson Klemencic Associates was the structural engineer with Arup. Arup also provided mechanical, electrical, and plumbing engineering, as well as fire/life safety, security, IT and communications, and audio visual consulting. Hoffman Construction Company of Portland, Oregon, was the general contractor. The 362,987 square feet public library has the capacity to hold about one and a half million books and other materials. It offers underground public parking for 143 vehicles and over 400 computers accessible to the public. Over two million people visited the library during its first year. It is the third Seattle Central Library building to be located on the same site at 1000 Fourth Avenue, the block bounded by Fourth and Fifth Avenues and Madison and Spring Streets. The library has a unique, striking appearance, consisting of several discrete "floating platforms" seemingly wrapped in a large steel net around glass skin. Architectural tours of the building began in June 2004. In 2007, the building was voted #108 on the American Institute of Architects' list of Americans' 150 favorite structures in the U.S. It was one of two places in Seattle to be included on the list of 150 structures, the other being T-Mobile Park.