I don't see how they can't teleport out of an encounter if they can in an encounter, but on to your point. I imagine Eladrin cities as akin to the Dagda of legend. They are both well-hidden and expansive, with delicate towers and bridgeworks hidden by glamours. The areas where other races might visit are relatively normal, with roads and paths and such; but the Eladrin only areas are full of hidden paths and illusory towers and walls. One second a non-Eladrin would see a hillock, and the next they would see the pale shimmering towers. At least that's the idea I'm working with, I need to do some refining.