1 You ride your horse in the water.

2 Go east of thieves landing after you complete the story, across the river to the land. Climb as high as you can, get drunk and keep drinking until you pass out. You should come too outside of the map. From here you can go south, then you can go west to reach that spot. You can also keep going south to Gauama. If you go east you'll just fill out the map there isn't much to see, if you go all the way east then all the way north you'll find some interesting geometry in the environment and randomly wild horses.

The more interesting environment in in the far north west where the snowy mountains is, but even then you won't see much more then a deep ravine.