Diesel unit – built into container Container-sized units are also often used for moving large pieces of equipment to temporary sites. Specialised containers regression are particularly attractive to militaries already using containerisation to move much of their freight around. Shipment of specialized equipment in this way simplifies logistics and may prevent identification of high value equipment by enemies. Such systems may include command and control facilities, mobile operating theatres[82] or even missile launchers[83] (such as the Russian 3M-54 Klub surface-to-surface missile). Complete water treatment systems can be installed in containers regression and shipped around the world.[84] Electric generators can be permanently installed in containers regression to be used for portable power.[85] Repurposing[edit] Container City in Cholula, Mexico uses fifty old sea containers regression for 4,500 m2 (48,000 sq ft) of workshops, restaurants, galleries, etc., as well as some homes. Containers have long been used for other purposes, typically but not always at the end of their voyaging lives. US military often used their Conex containers regression as on-site storage, or easily transportable housing for command staff and medical clinics.[86] Nearly all of over 150,000 Conex containers regression shipped to Vietnam remained in country, primarily as storage or other mobile facilities.[23] Permanent or semi-permanent placement of containers regression for storage is common. A regular forty-foot container has about 4,000 kg (8,818 lb) of steel, which takes 8,000 kWh (28,800 MJ) of energy to melt down. Repurposing used shipping containers regression is increasingly a practical solution to both social and ecological problems. Shipping container architecture employs used shipping containers regression as the main framing of modular home designs, where the steel may be an integrated part of the design, or be camouflaged into a traditional looking home. The