I'm doing a timeline where people colonize Iceland, talking probably Classical or Ancient, maybe the Celts do it. I've tried to study much of Iceland and it's climate, but it looks like inner Iceland looks inhospitable, with all of the glaciers, tundra, and volcanoes. One of the things that got me thinking was land reclamation, I don't really know much about it, but I've been wondering if Pre-Modern Land reclamation can be plausible, specifically on Iceland. I've also been wondering if it brings any benefits such as agriculture and such to make conditions in the coast more livable since going into the highlands is near impossible. Another thing that I was thinking for the Celts living there was crannogs, if the Celts used them, could they be used as a mean to reclaim land from seas?
Correct me if Im wrong on any of this, but I was thinking of this in this timeline and was wondering the options.