Generation Zero

If you've been playing this game on and off for a long while during patch phase you might not get the achievement due to a counter reset. Just go back and climb the light houses you've already been to again and it should unlock. Worked for me!

I've been to the top of four lighthouses and this has not unlocked for me. Hopefully there are a few more and it unlocks eventually. What a game...

I can confirmed the lighthouses on the DLC maps doesn't count.

. 17 Feb 2022
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Guide was fine.
I went to and climbed all 3 lighthouses and the achievement unlocked right away.

This hasn't unlocked for me either, I will go back later to all lighthouses again and see if it will unlock.

***UPDATE*** This has now unlocked for me what I did was re-visited the lighthouses and on the FOURTH one the achievement popped.

Climbed lighthouses at Arkelstorp (2548,-3805), Sillavik (-3600,4179) and Stenudden (1896,4650) and no achievement. Will report back when it pops as many achievements have popped well after the requirements have been met.
EDIT: After climbing a FOURTH lighthouse at Hisingafyren (-5642, 4515) in the far south west the achievement finally popped. Good job as there are only 5 lighthouses on the map!