Isn't it infinite? The world generator starts glitching after you explored too much, but still.
it is infinite, but a computer can only handle so much of your world. Again, it's randomly generated so eventually you'll run into the same thing again and again.
Daggerfall was the same way, that size ultimately was not that spectacular when most dungeons, caverns etc ultimately fitted into several different molds and that massive over world was literally dead-flat. Most major landmarks were sprites.