It's a bit more than that. It's not AT Via P. and Via I.N. - it STARTS at that corner, but extends quite a bit. You could walk for hours before covering the whole flea market (It covers at least a kilometer). It's known as Porta Portese - it takes the name of thegate (archway) where it starts (the opposite end of Via P. and Via I.P.) You have to get there very early (I used to go for 8:30am) in order to avoid the crowds which make it literally impossible to get through the usually narrow paths between the stands.

Laurie in Mexico City