Crossroads
Traditionally the crossroads has been a place of power. Suspected vampires were sometimes buried at a crossroads under the belief that the vampire would be unable to choose a direction in which to hunt for victims and waste the night trying to decide. Folk tales and folk magic would speak of summoning demons, or in some cases contacting fae or other supernatural creatures, at the crossroads. Some stories even tell of deals with the devil being made at a crossroads.
Of course, these tales come to us from an era in which a crossroads was a rare thing. These days, they can be found every few hundred feet in most countries. They've become so common that they have lost their associations and with them, their power. So where has their power gone? To the freeway intersection. Sure, one can get to a freeway intersection easily enough, but most of them are many miles apart. It takes effort to get to one, and they have great importance these days. Getting around in America at least requires making use of many freeway intersections. They have functionally filled the same role that the crossroads once did.
Now, if freeway intersections have magical significance along these lines, then places where more than two freeways intersect will be even more powerful. Think for a moment about the places in America that have many freeway intersections. Think about the kind of power that could be easily raised in a place like New York or Los Angeles.
It's just a thought.