I have health issues that make avoiding steep streets important for me. The problem with topo maps is that it's a pain in the ass to read them, specially in areas with lots of features, such as cities.

I like color-coded height maps, they can give you an intuitive feel for how a city lies on top of its terrain. It's very hard to make out moderate slopes though, e.g. if the city has high hills. I would most prefer a color-coded map showing the gradient.

Incidentally, if anyone has pointers to where this kind of map could be obtained (mostly for european cities in my case, but any resource would be helpful), I would appreciate it. Right now, I just try my luck with google when visiting a new city.