Also known as Earth West 1,617,848, and classified as "a typical arid Joker World", Rectangles is pretty much unique in the Long Earth. There is a massive pyramid, for one thing, and lots of evidence of a sentient race who were far more technologically advanced than Datum Earth. But they're all dead. The massive radioactive pile might have something to do with that. The inquisitive and acquisitive Kobold Finn McCool has discovered potentially powerful hand-weapons here (fortunately they are inert. Or seemingly so.) Lobsang and Sally Linsay took away matching rings. Which are important for what they might unlock about Rectangles' technology. The fact it is comparatively few steps away from the home world of the Beagles - an intelligent and above all warlike canine race - is also significant.