Earlier this year, Japanese artist Yasuaki Onishi filled the Rice Art Gallery with what seemed to be a floating mountain. Onishi, who uses a process he calls "casting the invisible," created the installation over a three-week period. He and an assistant first draped plastic sheeting over stacked cardboard boxes, then glued the sheets in place with black hot-glue, which was dripped down thousands of plastic lines hung from the ceiling. Onishi removed the boxes to leave a void. The effect was mesmerizing. Under the sheets was empty space; above the space was a torrent of what seemed to be black rain. Visitors walked around and through the room-size installation, marveling at the weightlessness of it and at the painstaking process that created it.