There’s more going on in a subway map than just tracing lines through stops. The most important quality of a transit map is that it be easily legible, even when glanced across a crowded rush-hour car. Looking at it, you should be able to figure out how this network of colored lines and pips translates to the real city outside, but geographic fidelity is often a secondary consideration.

Still, you might be surprised by just how inaccurate your local subway map is compared to the topographic truth of the city. Created by Benjamin Schmidt, an assistant professor of history at Boston’s Northeastern University who we’ve written about before, this visualization warps the maps of three subway systems to overlay their actual city grids.