One of the greatest things about virtual worlds is the fact that you can create anything. Usually, you get nothing but bare land, or water, and everything else --and I mean literally everything, butildings, plants, trees, furniture, grass, animals -- is created by you. Some of the artistry of these creations (or builds, as they are often called) is breathtaking.
There is currently a magnificently rendered mansion in Second Life in the region known as Belmondo. I say currently, because the site appears to be abandoned by the creator, and will most likely disappear as soon as Linden Lab, the owner of Second Life, discovers that the land is abandoned. I would like to urge you to travel to the Belmondo region in Second Life, and see this for yourself. If you are not registered for SL, here is a blog post which gives a few photographs of the place. (And yes, I mean photographs, for those of you who aren't familiar with the reality of being in a virtual world.) The blog post which is written by Tateru Nino, also has links to more photos. If you have the ability to travel to Second Life, here is the location of the build.
A tip of the blogger hat to Tateru Nino for pointing this out.