Misdirection!

My Command Center will have a heavily guarded room at the bottom of a 100 story subterranean shaft that will contain a sophisticated bus-sized computer with a fake encoded plan, no external link, and no real function whatsoever. The real command center will be a satellite-linked laptop on a card-table with a folding chair at the top of the elevator shaft, behind a door marked ‘standpipe valves’ accessible through the unlocked janitor’s closet.

via Evil Empress Guide.

This here is wise advise.