A Bell System ad from the late '40s claimed, "It takes 500 tons of equipment for just one telephone exchange" (that is, for the central-office connections among the 10,000 phone numbers sharing one prefix). As you may have noticed, electronics are a lot smaller these days. So, even with the explosion of phone numbers due to modems, cell phones, and fax machines, US West realized it didn't need all the downtown buildings it had inherited when Ma Bell was broken up. One of these buildings was extensively reworked (with exterior windows and other amenities added) to become the Hotel Monaco.