Complex sentence: The chamber is built on an enormous scale, its complex mechanisms indistinguishable from works of art. After a set of gigantic doors slam shut behind them, the three are then examined by a probing beam of light.
Split into simpler sentences: The chamber is built on an enormous scale, its complex mechanisms indistinguishable from works of art. After entering, gigantic doors sham shut behind them. The three are then examined by a probing beam of light.