Rocket engines are usually tested in large outdoor test stands far away from densely populated areas, where the engines can be left roar. Meanwhile in Russia, they build a soundproof and gas-tight indoor test chamber right in the middle of town.
Roscosmos, the Russian Federal Space Agency, has just posted two awesome photos of the altitude testing chamber at the headquarters of the engine maker Energomash, located in the town of Khimki, one of the largest satellite cities of Moscow.
Energomash is a leading developer and manufacturer of high-power liquid-fuel rocket engines in Russia. In this specific test chamber they can test their engines* without noise and dust, because it absorbs all the by-products of combustion.
NASA and ESA have similar huge chambers for simulating space conditions here on Earth, and Energomash also has dozens of other test systems, but this indoor testing chamber is unique. I would love to watch and listen to a recording from this chamber. Hey, Energomash, please put a few GoPro on those railings for our viewing pleasure!
*Engines such as the RD-180, currently being used by the United Launch Alliance (ULA) in their Atlas V medium-heavy launch vehicle.