Hey everybody! Just today I stumbled across a new place added in dawngaurd called red water den. It's pretty cool location that holds some exploration and a "quest" to complete. It is located in the rift almost in the middle of ivarstead and riften. It's located SW of boulderfall cave and SE of rift watchtower. If you don't see either of those places just head west from riften staying on the north shore of the water and it is a "shack/house" symbol on compass.

Oops my bad. Ive only played dawngaurd through on one faction, and it didn't cross my mind it could a quest on the other side.

This should be in the spoiler section.

And yes, it is on UESP.

http://www.uesp.net/wiki/Skyrim:Redwater_Den