Item from The Dresden Files by Jim Butcher
A scale model of Chicago Harry built in his sub-basement laboratory — a magical tracking tool that could locate anyone in the city, destroyed when his apartment burned down.
Little Chicago was a masterwork of magical engineering — a scale model of the city of Chicago roughly five feet across, built on a table in Harry's sub-basement laboratory. Every building, every street, every major feature of the city was represented in miniature, painstakingly constructed and magically attuned to its real-world counterpart. The model took years to build and required constant updating as the city changed — new construction, demolished buildings, altered streets all had to be reflected in the model for it to function accurately. The purpose was tracking. Harry could use a sympathetic link — a hair, a drop of blood, a personal possession — to locate anyone within Chicago's city limits. The model would show their position, their immediate surroundings, and allow Harry to observe them in real time through a magical projection. It was an intelligence tool of extraordinary value, effectively giving Harry surveillance capability over the entire city from his basement. Bob the Skull discovered a critical flaw in Little Chicago's design that would have killed Harry if he'd used it — the model's resonance patterns were slightly off, and activating it would have channeled enough energy through Harry to reduce him to ash. Bob fixed the flaw. Harry used the model successfully several times after that for tracking and surveillance operations. Little Chicago was destroyed when Harry's apartment building burned down. The model, the lab, and most of Harry's magical equipment were lost. Harry has not rebuilt it — partly because of the enormous investment of time and resources it would require, and partly because his circumstances have changed significantly since then.
A detailed scale model of Chicago's downtown, built on a table in Harry's sub-basement workroom. Every building, every street, proportionally accurate. Used as a sympathetic magic focus for tracking spells. Powered by a ley line running beneath the apartment.
Also known as: Little Chicago, the model, the scale model