The Green Palace, an imitation of Emerald City of Oz, is encountered by Roland’s ka-tet near the end of Wizard and Glass. Randall Flagg erected this along the I-70 thinny in the Alternate Topeka to taunt the ka-tet.
The Green Palace is entirely green and made of glass. The gate, made of twelve colored bars represent the twelve bends of Maerlyn's Rainbow. The broad central bar is black. All of the bars contain small creatures. The entire structure hums similar to a thinny.