Earth-3
From superman.nu: Supermanica
Earth-3
One of the countless Parallel-Worlds that Superman has encountered in his adventures (first appearance: Justice League of America No. 29, Aug 1964: "Crisis on Earth-Three"). This Earth's populace includes super-villainous counterparts of a select few of Earth-1's super-heroes, who have banded together as the Crime Syndicate of America, including Superman's counterpart--Ultraman.
