It sounds like Norwegians were involved in building this, and they have precedent for this look. "hardanger bridge roundabouts" is a search term which will get

It sounds like Norwegians were involved in building this, and they have precedent for this look. "hardanger bridge roundabouts" is a search term which will get you some pretty images for roundabouts like this. Admittedly they're not under the ocean, but they are underground at each end of the world's longest tunnel to tunnel suspension bridge. Underground funkily-lit roundabouts are pretty amazing!