You are looking at the IT infrastructure for this house. There are at least 4 network switches, an UPS, 14" CRT, and a bunch of cable spaghetti. It all sits comfortably under the plumbing for the rooms on both sides.
The server itself sits on the floor, just out of sight. Just follow the cabling down. Besides this website and email it runs a search engine for our network shares and plays music throughout the house.
I have spent quite some hours on those stairs, troubleshooting problems.