Crab Conceptualization

I've always liked the idea of a machine that can effectively replace cars in a certain situation. Cars seem like an almighty and obvious answer to our transportation needs, but what if our need were different? I can imagine a world/time/thing were cities are like islands, surrounded by deep jungles or deserts and without any transport communication in between. On such scenario, traveling between cities would be like a constant adventure as you would have to trespass untouched natural environments, and just like on the old days of exploration, the horse was the best vehicle available for this circumstances.
So, what if we had island cities, but the technology of modern times? Consider also that while flying its an "easy" answer, like 90% of today's cargo still goes through land or water. Touche!