Pyramus and Thisbe: Walls

The walls in Pyramus and Thisbe can be interpreted both literally and metaphorically. In the literal sense, the wall is the brick structure separating Pyramus's house from Thisbe's. The tiny hole in the wall allows Thisbe and Pyramus to murmur quietly to each other, but never speak or hold or kiss each other. For this reason, the two lovers become immensely frustrated with the wall, because it is preventing them from coming together. In line 73, Ovid writes "Invide paries quid amantibus obstas" which means: "Jealous wall, why do you stand in the way of lovers?" Through this line, the audience can feel the amount of frustration and bitterness from Pyramus and Thisbe, becasue of the fact that they are scolding a wall. Ironically, though, the wall provides the only means of communication between the two lovers.
Metaphorically, the wall represents the separation between Pyramus and Thisbe, according to their parent's refusal to their marriage. In line 60 Ovid writes "Tadae quoque iure coissent sed vetuere patres" meaning "They would have met in the bond of marriage, but the fathers forbade it." The fact that Pyramus and Thisbe's parents refuse to allow them to get married, for whatever reason, is preventing them from uniting, just as the literal wall in the poem is.
Another metaphorical interpretation of the wall can be the lioness that the two encounter, after they sneak out of the city. The lion is what separates the two lovers from uniting, though they schemed an elaborate plan to finally see each other.