From ArborWiki

The Blake Transit Center is a hub of the Ann Arbor Transportation Authority, located in downtown Ann Arbor. It is between Fourth Avenue and Fifth Avenue next to the parking lot at the corner of William and Fifth Avenue on the site of the Old YMCA, across from the Ann Arbor Distrct Library, and behind the Federal Building.

Buses arrive just before the quarter hour and generally leave at three minutes after the quarter hour; specific schedules for routes can be viewed on AATA's website.