Newgrange

One of the eighteen Astral Bridges, and Koba's guardian post — once a year, on the winter solstice, a beam of dawn light slips through the roof-box above the entrance and runs the full length of the passage to light the inner chamber, and that beam is what keys the site into Neterios.

In the game — the Roof-Box Beam task: the roof-box has shifted out of true, and the solstice beam is missing the passage entirely. Realign it stone by stone before the window passes for another year. Completing it adds Koba to your portfolio and unlocks permanent fast travel to Newgrange.