A GeoWall is a low cost interactive 3D stereoscopic projection system. It consists of a computer with a dual-output graphics card, two projectors, a rack to hold them, polarizing filters, silver screen, a pair of cheap polarized glasses for each user, and (optionally) one or two monitors. This can be put together for well under US$10,000, or bought as a turnkey system at a higher price from various vendors. There are equivalent systems under other names e.g. passive 3D display.