Get to the top of the temple was a mission in The Precursor Legacy that Jak and Daxter completed to obtain a power cell. An unassigned mission where Jak made his way to the top of the forbidden temple and found a power cell.
Enter Forbidden Jungle and head left, past the second bridge. Be careful of any lurkers or vines. Walk past the Precursor metal drums, the swinging logs and eventually you will reach the end. Daxter will point out the bridge here, so walk into the nearby blue eco vent and activate the bridge while channeling blue eco. Cross it, activate the door and once inside, you will have to use a few trampolines, some moving platforms (make sure to be charged up with blue eco) and a Precursor launcher to reach the very top.
There will be plenty of blue eco available throughout the route as well as another precursor launcher midway; near the end will be a lone babak blocking your path. The last part consists of two platforms slowly traveling around the tower; be careful not to fall off at this point as the impact will deal damage, plus you will have to go all the way back up again. The power cell rests on the top platform, which subsequently acts as a one-way elevator down into the Temple.