[Guardian]

(*) In RL cities it also depends on the density of the city. For example, in intra-muros Paris, that is a very dense city, the subway network was laid out in such a way that - with a few exceptions - no point in the city is more than 500 meters (about 1500 feet) away from a subway station. In more modern subway networks the distance between the stations tends to be longer than in older implementations.

Wow, I had no idea! That seems so short! Especially knowing the modern implementation of it.