I'm lifting this term Playa from its Burning Man context. That's an annual EPCOT-like experience wherein teams experiment with prototypes for tomorrow.
However, we don't see big engineering firms representing at Burning Man. Maybe some of their people join a crew, but you won't see pavilions from Boeing, Siemens or Google. That's a bit worrisome.
Sure, humans learned how to build geodesic spheres and domes in the 1900s, but did they ever attempt a really big one after Montreal, way back in 1967? Was any bigger?
We expect the sea levels to rise, and even if they don't, we might need to build whole cities from scratch for other reasons. What about that OMR design?
Old Man River was like a super-sized stadium in design, with or without the mile wide dome. That means terraced, like rice paddies, around the interior. The circular city could be built in sections, using giant A-shaped sections.
Were these ideas practical? One needs to experiment, and scale models don't always tell the whole story. Engineers need to try stuff, not just to get the physics right, but to learn the workflows and building techniques.
We're leaving all that to Burning Man apparently. Or research into large scale structures might be happening in places I don't know about. Does Google Earth block them out?