The more visible parts of the SWF above the ground include a weapons factory, which is heavily damaged by Allied bombings during the events of Return to Castle Wolfenstein, and a trainyard with an adjacent warehouse. Which make the entire part of Mission 4. The main facility lies hidden underground and that is where the most important research takes place. X-creatures like Lopers are probably created for weapon experiments, like the test for the Venom gun's firing rates.