Casey and Aucoin being the Hollow Men to the fore as they begin an excellent three part story in Adventures of Superman 614 (May 2003).
Batman appears holographically to Superman, informing him about a White House discovery of a forgotten military experiment from fifty years ago. And though his reason for contacting Superman is to get him on the case, he also has learned that Luthor is aware that Clark is Superman.
The Ray, recently a member of Young Justice, also falls victim to the Hollow Men.
Superman finds the concealed entrance to the tesseract that contains Heroville – most easily described as Pleasantville with super-heroes. And doesn’t that courthouse look like the one from Back to the Future?
Superman finds the man in charge, and learns that, back during World War 2, the government was experimenting with creating heroes. When the public opinion turned against costumed adventurers, and the Justice Society was forced to go underground, the people of Heroville entered the tesseract, where they have been ever since, in a weird little utopia. The government troops that Superman were looking for scared the people, who thought they were evil invaders, and they have been locked up, but otherwise unharmed.
Great artistic swipe as Superman and the doctor walk the US troops out of the tesseract, after dressing up like Heroville people.
But this is not a happy story, and the Hollow Men show up at the end. They attack the Elongated Man, but Sue Dibny manages to hide, and contacts the military to let them know. As the story ends, the Hollow Men approach Heroville.
The story continues in the next issue.