Tollen Dam is at least a century old, having been built sometime before Imulsion's potential as a high-energy fuel source was discovered by Dr. Helen Cooper. The dam was decorated with four massive busts, representing the four then-known sources of energy: air, water, solar, and gas. Following the end of the Locust War, the dried-up reservoir behind Tollen Dam was re-purposed as one of many burial sites for thousands of crystallized Locust corpses. Upon the emergence of the Swarm, the burial site and dam became the site of a large nest.