The enclosed area in the center was initially just filled with gardens. But they looked too generic, so I ended up adding bits and pieces, eventually extending past the row of education and entertainment structures. The small statues were literally last minute additions and I must admit I was pleasantly surprised by them.
BTW, big thanks to Marty Party. I usually check out his cities after I've finished a level and have greatly improved my playing (I hope) of this wonderful, wonderful game.