I'm interested in compiling a list of bookstores around the world that stock a good selection of high-level mathematical books. The aim is so that a mathematician travelling, or on holiday, can easily check the list to see if there is a book store nearby that she or he could happily spend an hour browsing in.

Some particulars:

 - It must be a **physical** bookstore.
 - It should have a good selection of **research level** books. This criterion is designed to exclude stores that stock primarily popular books and undergraduate textbooks, such as some university and chain bookshops.