I've toyed with the idea of the crossroads as a place of power several times in my games. It's a concept of modern myth that really intrigues me.
Today I was wondering why the most powerful crossroads depicted in popular culture always seem to be in isolated locations. A modern city is littered with grids of crossroads as north-south aligned thoroughfares intersect those going east-west. Why wouldn't a city be a place where thousands of demons are waiting to make pacts with mortals? Maybe they are.
But another option might be to consider the length of the roads leading to the crossroads. In the middle of a city, it might only be a few dozen metres (or yards) from one crossroads to the next, which isn't enough length for the incoming energies to generate much of a charge. In a rural environment, it might be kilometres (or miles) between crossroads, thus giving ample length for the crossroads to generate significant charge levels. If the charge level isn't high enough, there simply isn't enough to meet a threshold required for breaching the barrier between worlds. Thus, no inherent magical portals for summoning crossroad demons in cities. You need to use other means.
This may also explain why technocratic types are always trying to expand their cities, and carving new roads across the landscape...not only to expand their city based influence, but also to minimise the power that might be generated by rural crossroad hotspots.
Just a fragment of an idea at the moment.