In recent years, developers have pushed the envelope a lot.
3. Assassin's Creed Brotherhood
The original Assassin's Creed added so much to the open world genre with its liberal use of free running, but it was hampered by Altair's inexplicable inability to swim. Once we got control of the semi-aquatic Ezio though, the world seemed to open up a great deal more, and the addition of the Assassin's Brotherhood in the eponymous third Assassin's Creed game made Italy feel more expansive than ever.