Before the fall of Atlantia the Urania islands were a scientific research hub. The only surface settlement was an off-shore rig used as a port. The islands themselves were nature reserves.
The bulk of development in the Urania region was sub-surface, with researchers exploring the nearby undersea environment and making rare (and strictly regulated) expeditions to the otherwise untouched islands.
Frequent submarine trips kept the undersea bases connected, and the researchers of the area treated inter-settlement trips more like long bus commutes rather than unusual special or difficult.
The rig was a graveyard, filled with slaughtered people killed by small arms fire. The fission reactor of the rig appears to have melted down, likely due to sabotage, wreathing the island cluster in deadly radiation to this day.
The sub-sea habitats are largely unexplored for this reason. Though Dig-Lord-S6 Miningmechs are available to dig through the ice, the radiation makes extended operations hazardous. The spent reactor core has been retrieved and disposed of, but the area has been left abandoned since then while the radiation level drops naturally.