User blog:MasterCharmander13/I thought of doing something cool....have no idea how to

So Castela is the planet that we know most about in DWA(well...we know more of Gallifrey, but that doesn't count cause it's from RealWho as well), so I thought of this really cool thing.....CREATING Castela.

I was thinking that if there was some program(free), or some online site or SOMETHING that allows you to start off with a rotating blue(the water) sphere, and letting you add your own shaped continents and islands and stuff like that. Wouldn't it be cool to have a canon look at how Castela really is.

For the past weeks I've been searching for such a site or program, but couldn't really find anything. So can anyone help me find either a site, or a free program that allows such a thing?