    The common room was a large, square room decorated with the Slytherin colours of silver and green. There were several rather grand fireplaces made from white marble, and the stone floor was covered with thick green rugs. The seating was also elegant – black and green leather sofas and chairs were arranged throughout the space. There were lamps scattered around the common room, and several large glass windows that looked out into – darkness? Harry squinted. Were the windows looking out at the lake they’d sailed across to get to Hogwarts?