you've visited the Ibon del Cau. I thought that no one went there these days :)
Some people still do ! And the trail was newly marked when I visited it. Worse than you think, I even visited the sister branch of this Y valley on the way down (the one under the Barleto lakes). I think I will never do it again. If you wonder why, try to go to the place and have a look :)
We did it this year (the Cau part). The upper reaches were very broken-up after rock-falls etc. And crossing the water was ...er, fun! We've got Punta Suelza on the list for later this month so I hope I can see the lake from above this time!