The Comedy of Errors is set in the Ancient Greek city of Ephesus. Located near the Aegean Sea, Ephesus was the site of a large harbor in antiquity, thus serving as an important stop on trade routes through the Mediterranean. Shakespeare draws from this history in depicting Ephesus as a bustling commercial center, setting the ground for the play’s interest in markets, economic value, and exchange. A busy city is a fit setting for this play, creating many opportunities for characters to come and go, bumping into one another while going about their daily business.
Another important aspect of Ephesus as a setting is its rivalry with the city of Syracuse, where Aegeon and Antipholus of Syracuse have lived since their family was divided. As residents of Syracuse are not allowed to enter Ephesus due to political tensions, Aegeon and Antipholus of Syracuse have taken a real risk in sailing to Ephesus to reunite their family. Within the city, the play is set in three locations: a marketplace, a priory (or, in other words, a monastery dedicated to religious devotion and meditation), and the home of Antipholus of Ephesus, which is further subdivided into an indoor area and an outdoor area. In many stagings of the play, all three locations are visible on stage at all times.
Not only is the play set entirely in Ephesus, but its story also takes place across the span of exactly one day, from morning (when Aegeon is sentenced to death) to evening (when his execution is scheduled to occur.) The Comedy of Errors, then, satisfies the three classical unities, sometimes called the Aristotelian Unities (time, place, action), which served as an artistic ideal for theater in the Renaissance. Only one other Shakespeare play—The Tempest—satisfies the unities in staging one principal storyline across a period of time no longer than one day, in one single location.