From the publisher's website:

Since the dawn of history, people have come to cities – to visit, to pass through, to stay. And bustling streets provide opportunities for adventure.

GURPS City Stats offers cohesive rules to define a city’s impact on adventurers. A new stat block provides a compact way to write up a city, just like a character, vehicle, or planet. Guidelines for using urban regions in your campaign suggest how to turn them into exciting encounters or challenging places to live.

City Stats also includes stats, descriptions, notable residents, and campaign options for four sample locations suited to different types of campaigns: Athens (historical), Tredroy (fantasy/GURPS Banestorm), San Francisco (modern), and Pavonis Portal (science fiction).