The crystal control room.

The Crystal control room was a central structure under the Onrai square in the main city on Seoul 5. It was the source of power for the entire city, due to its stock of Seoularian crystals. However, a short time before the outbreak of the Galactic Civil War, an Imperial scout removed the main Key crystal from the room, which was used to control the powers of the other crystals.

A short time after the Battle of Endor, Imperials under the command of Captain Drezzel discovered the city and the crystal control room. The xenoarchaeologists Fem Nu-Ar and Xathan who had accompanied the Imperials to investigate the ruins were eventually imprisoned in the control room for objecting to the Imperial plan to use the crystals for new Imperial weapons. They were rescued by Han Solo after he obtained the key crystal from the Imperial scout in a card game. In an odd turn of events, Solo inadvertently used the key crystal to overload the other crystals, causing the control room to be destroyed