CERN. In 2004, I think. Everything was beige in that world; floors and ceilings, tables and chairs. The concrete and the melamine. The computers. The end of one passage did, however, lead somewhere unexpected.

At the foot of a short flight of stairs, a perfectly ordinary set of double doors opened into a long subterranean tunnel¹ that had fallen into disrepair. Here sagging cables lined the ceiling,² the walls were stained and damp, and pools of standing water reflected the flickering florescent light. As you stepped out onto the metal walkway it shifted underfoot...