The Lost City - Climbing to the Second Trebuchet

Head for the northeast corner at the top of the stairs leading out of the ambush area. Shoot a rope arrow into the dangling spool to swing across the gap onto the ledge ahead.

You're headed for the trebuchet to the northeast, but there's a rope-wrapped barrier on the right that you can pull down to open the way back to the Citadel Plaza Base Camp in case you need to rest and resupply. Also, the last statue (8/8) for the Vandal Challenge is sitting on top of the building above and to the left of the barrier. Destroy it to complete the challenge and receive an XP award plus 2,000 Expedition Credits.

When you're ready to move on, return here, slide down the zip line and latch onto the ice wall below. Then climb up to the wide ledge below the trebuchet.

This area has a rotating beam with a golden bucket suspended from it. Ahead on the left is a wall of ice.

Before tackling the mechanism, scramble up onto the wall on the left...

...to find an Archivist Map (3/3).

Drop back down and face the rotating beam. Use a rope arrow to pull the bucket around to the left.

Then run up the wooden ramp and jump onto the bucket...

...to send it crashing into the ice wall. (Remember doing this waaaay back in the Ice Ship Challenge Tomb?)

With the ice cleared away, you can now shoot a series of climbing arrows into the soft wooden wall and use them to climb to the top.