Complex sentence: The Pavilion hotel was rebuilt, adding two full floors, an attic floor below its new fashionable mansard roof, two new ball rooms, dining rooms, lounges, all lit by gas jet.
Split into simpler sentences: The Pavilion hotel was rebuilt, adding two full floors, and an attic floor below its a fashionable new mansard roof. Two new ball rooms, dining rooms, and lounges, were all lit by gas jet.