These designs were done for one of the five DC direct to videos that I contributed to while at Warner Brothers.
Superman's Fortress of Solitude.
I've always felt that the interior of Superman's Fortress of Solitude should feel more like a place of sanctuary as well as reflect more of his Kryptonian technology. Maybe you'll disagree, but having a space dominated by giant angular crystals isn't my idea of the ideal place for retreat and relaxation.
The open air battle arena on Apokolips.