This is Uzbekistan’s solar furnace, built by the Soviets in 1981 on a mountain range 50 kilometers east of Tashkent.

The site was top secret during the Soviet period and remained tightly guarded until 2009.

The furnace uses sunlight to produce clean, instantly adjustable heat for melting or testing materials.

The power for the furnace comes from these 62 giant mirrors that swivel to bounce sunlight toward a vast "concentrator" dish.

A window in the center of the concentrator, which is made up of 10,700 chessboard-sized mirrors.

The concentrator dish focuses the sunlight onto a point the size of a large wok.

Between 11 a.m. and 1 p.m., when the sun is at its strongest, the furnace can blaze at a ferocious 3,000 degrees Celsius – easily hot enough to liquefy iron, steel, and even titanium.

Ceramic parts are also produced in the facility. The furnace was “the leading facility of [the Soviet Union’s] military-industrial complex for [the] testing of different materials and equipment [with] concentrated solar radiation and for [the] development of advanced ceramic materials for high-tech industry.”

The furnace currently takes industrial orders from Uzbekistan and abroad, blazing to life around 100 times each year.

Javohir Zafarovich, a researcher who has worked at the facility for 21 years, demonstrates the power of a miniature concentrator in the facility. Within a second or two the stick popped into flames.

A 3.5-ton glass chandelier hanging inside the facility.

A researcher analyzing material samples. Around 160 people still work at the site, down from around 1,500 during the Soviet period.

Sun-themed art stands inside the facility, which has its own bomb shelter.

A mothballed miniature library that once held research literature from the Soviet Union and abroad is still on-site. Uzbekistan's solar furnace is the second of its kind in the world. The first opened in France in 1969.

The view from an upper deck of Uzbekistan's concentrator. The furnace's location was chosen partly for the single, solid lump of bedrock that it is built on. The rock plate insulates the finely tuned apparatus from the dozens of seismic tremors that rattle Uzbekistan every year.

Some of the giant mirrors of the facility wait in standby mode. The location was also selected for the hundreds of days of sunlight the site enjoys each year and the clear mountain air.

A warning sign at the base of the concentrator written in three languages. Surprisingly, the highest temperatures at the furnace are achieved on bright winter days when the air carries less dust and moisture than in the summer.

A bird wheels in front of the concentrator as the apparatus rumbles to life. Asked what happens when birds fly close to the focal point of the furnace, Zafarovich grimaces and replies: “Barbecue.”

A bank of mirrors swivel light toward the concentrator as the furnace operates. Zafarovich says the main advantage of the solar furnace is the total purity of the heat -- unlike fuel-powered furnaces that generate smoke and other impurities -- and the ability to instantly change temperatures.

A worker goes up the stairs in the facility. The disadvantages of the solar furnace are more obvious, as cloudy weather can leave the furnace idle for days on end.

Workers near the sensor (center of photo) that monitors the inside of the furnace as it operates.

An elevator shaft at the rear of the concentrator. The dish at the top is an architectural flourish and has no technical function.

A worker in the superstructure of the concentrator.