The Roma Scenario developed to 15k population with perfect stats.
It's not so difficult to build the population to 20k or so, but to get to 15k with perfect stats is harder and quite satisfying to achieve.
There are 29 Grand Mansions in this city, and very little employment imbalance.
The city was developed organically, with the general idea of growing anticlockwise from the immigration point, over two bridges at the island, around the central hill. There are several poorly laid out areas, but that's ok as long as they work to keep the stats at 100.
I dislike regimented layouts and designs, preferring to let the city grow under some simple general planning rules. Perfect symmetry is unnatural.
Actually the population is just 30 short of 15k. There are lots of ways of pushing it up to 15,000 or more, but to do it without causing Culture or Prosperity to dip below 100 is tricky. Please have a go!