Skyrim Sidelines- Bloodlet Throne: Seeking the Predators

This dungeon is located in the Southern part of Falkreath Hold, and is notably a vampire dungeon- anyone sending you out to kill vampires or retrieve something from vampires may send you here.  The ruined tower/fortress that composes the dungeon is in a rather obscure location, and requires some walking to get to.

If you've found Pinewatch, that's a good starting point- if not, look for it.  The location is to the East of Falkreath, along the road that passes under the bandit rockfall traps.

From Pinewatch, head West by Southwest until you reach the stream that ends in a rocky pond.  From here, head up the most obvious traversable slope and you'll find yourself climbing the Southern mountains of Skyrim.  Continue until you find a wide, vague trail through the snow upslope.  This is your route, and it's one that's not marked well from most other locations.

The trail has a number of switchbacks as it climbs the mountain, often difficult to find- keep up the most walkable-looking directions, turning to find them when needed, and you'll usually be right.  A good sign is when you reach the two cairns with ragged flags flapping from them on either side of a rocky section of the path.  If you pass these you know you're in the right direction.

Further on up the path you'll see a vein of Moonstone- rather than walking alongside it, turn and head uphill as you near it.  Several bear traps will be lying in the snow to your right, and if you continue past them you'll come to a large somewhat level area off to the left of the path.  Continue on the path and you'll find the stone ruin, nestled in amongst some trees.

Before entering the vampire lair via the door, get up onto the roof where the building sort of merges into the rising slope of the ravine and you can climb up into the shattered tower.  Here you'll find a chest with some potentially useful contents, as well as a bow and arrows that may be of some value.

If you come down the far side of the building, you can also locate a vein of quicksilver ore against the wall and another at the edge of the ravine (thankfully, the vampires don't really seem to do any patrolling outside their own lair).