So, for this story I'm drafting, I want to use this type of landscape for the main region where the plot develops.
Basically, instead of a sea of water proper, the islands are low valleys amidst steep mountains.
My question is, is this a possible structure in the real world? And what would be the consequences on the climate of the areas?
Edit: It was two part but I decided only to ask about part of the problem. Correcting it now. The Isles, the name of the place, is supposed to an archipelago. The terrain of these Islands are fertile valleys surrounded by steep mountain.
Basically, the Islands are made of a series of low mountains surrounded by higher ones, themselves surronded by smaller ones lower than sea level. All forming a single are called the Maw.