Locks and Dam 15 is the largest roller dam in the world at 1,203 feet in length. It was the first complex of the 9-Foot Channel Project and is unique because it consists entirely of roller gates, has different sizes and types of roller gates, is not perpendicular to the flow of the river, and is one of few locks and dam with a complete auxiliary lock. Mississippi River Visitor Center is located at Locks and Dam 15 on Rock Island Arsenal. It offers an observation deck which is a great place to view wildlife and the locking through process. The Mississippi River Visitor Center also offers tours of the Locks and Dam and a seasonal Bald Eagle/Clock Tower tour among others. Rock Island Arsenal is an active military installation, and all visitors must undergo a background check and be issued a pass to enter the island.