Now free to establish the city of his dreams, Batman brought in a bunch of settlers, set up shop, and named the place Gotham City. Ha, just kidding! He decided to take the "8-year-old naming his tree house" route and dubbed the city Batmania.
His entire Rogues Gallery was spider-themed.
Despite sounding like a combination of an Adam West wrestling show and the aftermath of a rabid bat attack, Batmania was off to a good start. However, a rival land plotter called Richard Bourke soon saw that Batman was on to a good thing and decided to swoop in, presumably in full Joker makeup. With the backing of the government, Bourke ripped up the treaty and started taking over the city. Batman did not like it one bit, but since the city was becoming the regional capital and Bourke happened to be the governor of said region, the Australian government put its foot down and basically told Batman (and the Aborigines) to eat a great big bag of platypus dicks.
In 1837, the new, Batman-free arrangement was made final, and the city's name was changed to honor the prime minister at the time, the Second Viscount of Melbourne.
Who at least had the decency to be called William Lamb and look like a mutton-themed Batman villain.