Its pretty common to get meadow, forest, mountain, plains and swamp within a 5 min walk of a central spot. Typically, out of necessity, one or two of those will be rather small; one place like that the swamp part I could jump across the whole biome but it would spawn leeches and other stuff on occasion. And there are on occasion crazy long (almost 1/3 of the map runs) land masses that have it all, but it may as well not because the sheer distances are too far to walk -- a portal on the same island or on 6 islands is the same in the end and boating is much faster and easier in general (noobily mishaps aside).