What's wrong with them? Well, "normal" sizes for rings in organic chemistry are 3, 5, 6 and 7 carbon atoms. 3 carbons form a triangle, which is thermodynamically unstable because of the strain in the bonds (carbon atoms with all single bonds usually have bond angles around 109.5 degrees, and in a triangle they're closer to 60 degrees) - but common in nature, especially if stabilised by some other rings adjacent. 5, 6 and 7 carbon atoms are stable because there is no ring strain, and form very easily because it's a relatively small number of carbons to have to wrap around to form the ring. As the number of carbon atoms increases, the probability of ring formation decreases, because it's too far for the first and last carbons to "find" each other.
By the time you're up to a single ring of 13 carbon atoms, the molecule looks quite ludicrous. It looks to me like a normal molecule with two 6-membered rings, where someone's taken one of the rings and pumped it up with a cycle pump!