Powell’s Books, Portland, Oregon.
Located on Burnside Ave in the Pearl District of Portland, Powell’s City of Books takes up an entire city block, and then some. The store itself is made up of three floors, with nine rooms that are each assigned a color and category of books. Getting lost inside is easier than you’d think, and happens often—often enough, at least, for them to have an iPhone and Android app that will act as a map.
There are several other locations of smaller Powell’s stores, but the one in the Pearl is the spot you have to see before you die. You can walk for an hour and still find a corner you haven’t been in yet. Not to mention the coffee shop, the art gallery, and the Rare Books room that’s open on weekends.
Literature heaven has a website as well: http://www.powells.com/