When all four shields are beneath the orrery, it is lifted away from the ground, revealing a deep shaft that leads straight into the depths of Aeternis, to the Grail sanctum. Mind the spikes at the bottom.
This is the orrery with a giant shaft. There are spikes at the bottom and dodging them is advised. To continue, jump down the dark hole. Don't worry, it's safe.
- Note from Geffrye: On the beams.