Enderal: The Shards of Order has a country almost as big as Skyrim filled with new quests, dungeons, monsters, and fully voiced English-speaking NPCs (some by professional voice actors). While the starting area is a traditional green heartland full of bandits, wolves, rats, and spiders eventually I find a dangerous jungle and stranger locations like a town built on platforms suspended above a water-filled cavern, or the Whisperwood with its glowing trees and crystal formations. There are mountains and snow as well but it's more obviously varied than Skyrim, even if the suddenness of its geographical changes can be jarring. They've also tweaked some of Skyrim’s fundamentals.
Source: The Game Website.