I don't think that's a cave. If you look closely, you'll see a train passing by, I think that cave is a tunnel entrance for the train to come and go. On the other side, the train goes over the bridge. I'm loving the town image though, it leads me to think the town will be much bigger this time out. You can even see a little house by the beach with a dock, an island to go to and various other small objects in the water. As for the town, there seems to be a commercial district and all the way at the top I would assume would be the town hall and museum.
One thing that has me wondering though is, given this image of the town was released, is everyone going to have a set village as apposed to a randomly created one. Given that we have freedom to affect and change the village to our liking, I wonder if they are placing everyone with the same starting layout and its up to us to change it and make it unique. All this has me even more interested and excited for this release now. It seems like they are finally expanding on the AC concept even if it's not to the extent that I would like (add some damn sports competitions like tennis and golf to the game, along with board games and interactive items, that would complete this game for me)