Here's a pic of the Wilhelmstadt area at start. My plan is to build some light industry towns on the upper land area and some resort towns on the lower. For the start I decided to build just one resort town adjacent to Spandau.
I started by extending one of the avenues from Spandau. I saw it was going to run right against a pond so I routed it a little south to go around. Then I decided to put in a little neighborhood in the triangular area between the pond and the canal dividing the land areas, like so:
Next I wanted to put in the elementary school so I would know where I could put residential developments (all Sims should have a primary school education; I'm sure it's in the the United Sim Nations Declarations of Sim Rights). But, I found the little neighborhood fit with an elementary school in the north areas, not the southern area I had planned to start with. Whoops. So I have to do the upper town first.
I laid in a mostly-residential area at the western tip for the start. Then I had to think about how to do the railroads. I wanted one going east to the one large area on the region map, where I'm thinking of making a railroad nexus. I also needed one going up to Tegel to link up to existing areas. I decided to make the one going east a straight shot while the one to Tegel would be diagonal and then go north. They would both connect to a station on the east side of my first town.
I started the game up and things developed pretty well. Here's a pic of the industry town:
While that was developing I laid out the resort town. I used avenues and large blocks to continue the adjacent section of Spandau. While I was working I got the Resort Hotel award and I put it next to a beach next to the river. I zoned 2 4x4 commercial areas and they developed into malls, which is a good fit. Otherwise I used a commercial-residential mix. Later I plan to put more beaches along the southern shore. Here's a pic of the resort town:
And here's the region pic.