This is a scene from Virtual Philadelphia, which you can sign up with and download at http://www.geosimphilly.com .
It has a good bit of detail in the area I’m in.
There are cars and trucks driving by, and avatars, though I don’t know if the avatars represent other users or are NPCs.
It’s kind of sluggish on my system.
There’s a walk mode, a hover mode, a fly mode, and you can choose to jump or fly to places by right clicking them and selecting jump or fly.
Everyone interested in virtual worlds should certainly give it a try.