
The entrance to Heaven, at the end of a rainbow bridge, as seen in "Karen's Priticoul Game".
Heaven is a desirable place, protected by a gate. To reach heaven, one has to cross a rainbow bridge. ("Karen's Priticoul Game")
According to the The Story of Day and Night, it's the home of Angels and God. Adam, an Angel, was originally from Heaven, before he asked God if he could see Earth. He would end up spending the rest of his days there. (Soul Symphony: "Genesis" - "The Story of Day and Night")
Heaven was also home to the Archangels, before Archanglea. Zesodis the demon was able to break through the gate to Heaven, where he was confronted by Archangels. He later escaped with an Archangel called Bob. (Archangel Saga: "Creation Of Zesoids" by Epic Worlds PCG)