The task is to climb your way to the top of the three tallest buildings in New Marais. This is a pretty easy mission to accomplish if you know the secrets behind.
Below are some tips on how to do so:
1. Locate the clock tower.
You will notice the clock tower when you are asked to get the first dead drop.
Just work your way up.
2. The next stop is the Cathedral.
Sneak inside and kill the guards on duty.
After taking the guards down, turn left.
Now climb and try going up to the top.
3. The last building is the ice tower.
Hint: It is safer to go there if you’ve finished the Powering Up Gas Work mission.
Try to go on top, just keep climbing.
Hint: The ice is very slippery, so you cannot accomplish this mission if you insist on climbing on it.
Hint: Look for another alternative.
Climb up the pipe instead.
Go for the next pipe. Basically go pipe for pipe until you reach the top.
When you reach the top, a few seconds later, you will receive the Mountaineer Trophy.
4. You can achieve another trophy by jumping from the top of the icy tower and then performing a Thunder Drop.
Wait a few seconds after you do this and you will see that you have achieved the Thunder Flop Trophy.
You can see the full video about the guide here: