Survey Island was an island on the Age of Riven. Gehn used equipment on this island to track Riven's slow breakup, and to keep an eye on his subjects living on Jungle Island. As with most of Riven's islands, access to Survey Island was restricted to Gehn and his closest followers. Two maglev tracks connected the island to its neighbors; one led to Jungle Island and the other to Book Assembly Island.
Survey Island was a stark and largely artificial landscape. It was divided into four main regions: two lower ponds on a plateau, an upper pond, and a large cavern. The first lower pond was shallow, and featured large, sharp rocks jutting out of its center at odd angles. It sat above the first maglev station and the access elevator to the cavern. Gehn ringed this pond with wahrk tusks, using the Rivenese people's fear of the creature as an added security measure. The second lower pond was at a slightly higher elevation. It too was a shallow body of water. A set of five artificial mesas in the shape of Riven's five primary islands were built atop it. These were themselves covered with a shallow layer of water, which could be heated from below by metal grates. When heated, the grates pushed the water up into forms that roughly resembled the contours of the associated island.
The upper pond sat in an elevated natural depression that had been fronted with stone on its southern face to create a square fortress-like structure. A giant dagger jutted out horizontally from this stone wall. An elevator connected this pond to the ones below. Within the pond was the island's firemarble dome, as well as a second round, domed metal structure. This building had an open interior with a mapping device at its center, which could be used to display small segments of one of Riven's islands using a Pin Art-like relief. The island being displayed was controlled by a panel at the end of a catwalk hanging from the huge dagger, just opposite the map room.
Beneath the island was a large cavern, which could be accessed by taking a gold-plated elevator down beneath a small pool of water that was held aloft by the heat of a magma chamber just below it. Inside, Gehn built a massive window that looked out into the ocean, and placed a "throne" atop a large stalagmite in the center. This chair was equipped with two observation devices: the first could be used to monitor the villagers on Jungle Island or Catherine on Prison Island, while the second was connected to a series of cameras that monitored the integrity of the various pipes that sent power to Gehn's firemarble domes.