Area 12 is a division of the Nevada National Security Site. It occupies approximately 40 square miles (103.6 km²) along the northern edge of the NNSS. At 7675 feet (2,339.3 m), the top of Rainier Mesa is the highest elevation within the NNNS.

Area 12 held 61 nuclear tests between 1957 and 1992, one of which involved two detonations. All tests were conducted below Rainier and Aqueduct mesas.

Area 12 was the primary location for tunnel tests and used almost exclusively for that purpose.

There are a number of tunnel complexes mined into Rainier Mesa that are used for experiments, including the E-, G-, N-, P-, and T-Tunnel complexes.
The Area 12 Camp was renovated and upgraded and provides a secure base camp for military units and other government agencies for conducting counter-terrorism and other exercises in the northern region of the NNSS. It provides an urban terrain setting utilizing existing commercial, residential, and industrial buildings. The camp includes 200 dormitory rooms, a cafeteria, weapons and munitions storage, and numerous operations and support buildings. The Office of Secure Transportation

Office of Secure Transportation

The U.S. Department of Energy/National Nuclear Security Administration's Office of Secure Transportation provides safe and secure transportation of nuclear weapons and components and special nuclear materials, and conducts other missions supporting the national security of the United States of...

uses it as a training facility.