The library ended and opened out into a big, round open space that had a large armillary sphere hanging from the ceiling, constantly turning as it depicted the dance of the sun and the moon around the world. Work benches covered with stacks of paper and discarded experiments bordered the sides of the room, while at the end was a big, concave window held together with solid lattice of iron-work. This was the source of the cold blue light, and quickly caught Twilight's attention. She ran over to the window and pushed her face up against it, trying to figure out where they were. There wasn't much to see as a blizzard was blowing outside, but she could just about make out nearby mountains. Judging by the way she was looking down at their bottoms, she could only conclude that they were inside another mountain.