Circle round once more... Perhaps it is different now... infinite glass wall...
Inspired by of course a goldfish swimming around circles and it's bowl...I had several goldfish in bowls for a little while until I determined that it was too tedious to clean each individual bowl and bought a large tank to keep them in ...they were so happy to be transferred into the tank that they swam around together for quite a while after being reintroduced to each other.
This can also be read figuratively as sort of the futility of rote dull work... I don't know pretty much everyone's felt trapped in an invisible shell that they feel like they're running circles around in occasionally...