Bairaktaris has stood on Monastiraki Square since 1879 and is the place to come for souvlaki and gyros after a long day at the Acropolis. The shop occupies two corner buildings and serves both as a counter takeaway for the standard pita-wrapped souvlaki and as a full taverna with table service on the outdoor terrace.
The food is solid rather than transcendent and the prices reflect the tourist location, but the location, the consistency, and the institution-status make it a reliable stop. Look for the framed photographs on the walls — politicians, actors, and footballers eating souvlaki on the same outdoor tables you are sitting on.