Favorite Bookstores

Recommendations for bookstores for out-of-towners.
I have had occasion to do a bit of traveling lately. When I reach my hotel, I pull out the phone book and look under 'Books' (and related headings) in the Yellow Pages. I write down the addresses, phone numbers, hours of operation of selected bookstores, and then try to determine their general location on the map given to me by the car rental company. Then, when I have time, I try to find these places. I usually don't make it to even half of the ones I select, and a lot of times, they weren't worth the trip anyway. Occasionally, I find a real gem.
What I'd like to see this Group become is ~THE PLACE TO GO~ to cut out a lot of the work I described above.
I want to know where you found that most treasured tome. Which bookstore has the best atmosphere for spending hours browsing the shelves? Which place has the best selection of books? What is your favorite place to get (insert-genre-here) books (there could be several...) and why? I'm interested in "places to go", not "places to avoid".
PLEASE BEGIN EACH SUBJECT LINE with State, City, Bookstore -- Later on, you can then click on "Topic" heading, and they'll all list geographically for you.
Of course, that presumes that the majority of posts will be for bookstores in the U.S -- otherwise, begin with Country first. Then feel free to rave to your heart's content.