Rem Koolhaas and Joshua Prince-Ramus finished this in 2004 and it remains the most interesting building in Seattle: a stack of shifted glass-and-steel platforms that reads as faceted from outside and genuinely strange inside. The Books Spiral runs the entire non-fiction collection up four storeys in one continuous ramp with no breaks between floors. The red corridor on level four and the tenth-floor reading room are the two things to find. Free, and a working library rather than a monument.