Being a geek, I get a kick out of checking out the local Bell Telephone central offices (COs), most which were built in AT&T divestiture days (pre 1984). This site has some cool pictures of the local COs.

Ma Bell used to build 3-4 story buildings, usually very ornate, to house their switching equipment. Nowadays, the telephone switches are all digital and take up very little space. Back in the 1920s-1980s the switching was done by electromechanical switches usually several stories high. When you would make a call, the machine would connect your circuit much like when they had an operator – by physically connecting things together. The arms of the machine would slide up and down to where your slot was and connect your call. An old AT&T employee once told me a story of the Birmingham CO in 1968 after the Tigers won the Series how the groud outside actually shook from the switches moving so much.

Some of the more ornate COs are located:

Downtown – the building with the AT&T logo on the west side of downtown
North of midtown and east of New Center – a large yellowish building
Corner of Mack & Cadiuex – a strange (mostly) unmarked building opposite of the National City branch that serves the pointes.
Downtown Royal Oak – just east of Main Street