As we know Mesa biome is new terrain has been update in the version 0.9.0 of Minecraft PE. This seed is new type of terrain seed in the version 0.9.0. You spawn in the mesa biome. Simply, this seed is a mesa biome with surrounding with flat landscape biome and a nice river flow through it.
Seeds : willyrex Work in PE ver0.9.0+ or ver0.9.5