For me, with 30 hours of slowly exploring the world under my belt, it has to be Eldergleam Sanctuary. I never expected to see this sight when I ran down that winding cave entrance. It's jaw-droppingly gorgeous.
http://cloud.steampowered.com/ugc/631856881956676893/7008875805255C3B99AB05F0C8A2A834D3893053/
http://cloud.steampowered.com/ugc/631856881956674699/5B405C991BD206CB611D62F7AB01992A36F387B0/
http://cloud.steampowered.com/ugc/631856881956672292/20993EEB0EB233057A8FECFE24C4204DF60C4E4F/
http://cloud.steampowered.com/ugc/631856881956669988/BFE3624E89DB0BC59F203560EF8B3DB118F212AA/
Be my guest to supply screenshots, but be wary of locations that might contain spoilers.

