This is part of what my playground map (or those that don't think my map is a playground, then it's a map in which the player isn't forced to solve puzzles) looks like. BTW I found out grass is portalable! This map is far from finished, but what I'm going for is a Portal 2 themed city, with robots that live in the city and test the Portal Gun for GLaDOS.
Here are the pictures:

The architecture does not look interesting.

Be creative, and design the buildings in visually interesting fashion.

If this is a playground map, make sure it has a whole lot more portalable surfaces before you release it. It's just a generic playground if you can't put portals anywhere. Also make sure it's co-op and single-player compatible.

I agree with satchmo. I think with Portal 2 you get used to making blocks... in Half Life 2, TF2 or CSS, when you make maps you have to think about doing cool architectural designs, interestingly shaped streets/back alleys/pretty environment shadows/etc. If it's going to be a city, go ahead and do that. Some of the Portal 2 textures would fit pretty well, and I'm sure it wouldn't be too hard to port in a few of your own textures or some HL2 textures to make it feel a little more city like until you go inside the buildings and it's suddenly a test chamber.

This is just one of the buildings I'm making. I'm still working on the Robot Dancing Hall. I realize the the buildings are going to have to look like buildings. These are like temporary textures that I'm using. However, this is a city GLaDOS made, it's not going to be made of bricks or wood. And not all of the buildings are going to be test chambers. There will be some grass fields. The grass is portalable, in case you didn't read my last post.
The road is just there as a landmark for now. When I start expanding the map, the roads will lead to other buildings. And I will also work on the sewer which will be accessed via manhole or a gutter on the street (which also lead to a few locked rooms). Back alleys will contain LOTS of drawings on walls as well as some hints on what to do to achieve the goal.
The isolated area away from the city is still under heavy editing. I'm trying to make it worth exploring, while trying to make it seem a little creepy. I can't go into much detail about it because it is a vital part of achieving the goal in the map.
Since I never really mentioned what the goal is I'll tell you that it will involve a boss battle in the city, but that is as far as I'll go for spoiling it.

BTW: Houses will be easy to tell apart from test buildings. If fact, houses will act as "checkpoints" in case the player dies and doesn't want to walk or portal all the way back to the place they died.

Edit: More pictures! Got the Robo-Disco Building to work. Still got some things to work on, but expect to see more dancing robots in the room.

What I would love to see would be an arcade, using some game_ui entities to make the machines playable!

You brought this topic back from the grave. This map is currently on hold till I get more ideas.

YM_Industries wrote:
What I would love to see would be an arcade, using some game_ui entities to make the machines playable!

^

MasterLagger wrote:
You brought this topic back from the grave. This map is currently on hold till I get more ideas.

I had actually considered making an arcade map with things like pinball, using spheres, hard light bridges, etc. Could be fun in your map.