During the transition effect which shows us that the story line switched to another Universe, it is very easy to spot a big difference between the Fringe HQ here and there. Specifically, there is a different building on the other side which somewhat resembles a Roman arena.
What kind of a building is that? Was it a proposed project which was never finished (in actual real life Boston)? Or was it just something that writers made up to stand out and look obviously different so that we could more easily identify which universe we are watching (like airships and the bronze colored statue)?