User blog comment:PinkFlyingBunny/Thalia Kidnapped?/@comment-4528975-20111219032637/@comment-4528975-20111219160716

After Hera got freed she probably talked to Zeus and made him open Olympus again. The Son of Neptune was eight months after The Lost Hero. It wouldn't make sense if Zeus didn't open Olympus since there's a war going on and the Gods need to get busy and help their children.