If you want to see the Rastro market you have to go on Sunday. There is no market any other day except on other official holidays (15 a year). It's open from about 10 am to about 2.30 pm. It's probably less crowded first thing in the morning, but more fun as it gets closer to closing time when everybody starts heading for the bars. Any other day of the week it's nice to stroll around the side streets where the permanent junk and antique shops are. You may overlook them on a busy Sunday.