I grew up enjoying the SimCity series. Later, Cities: Skylines brought me back to the same pleasure: watching roads, neighborhoods, and a city of my own grow from an empty piece of land. I kept wondering what would happen if that experience met the terrain of real places.
BuildBuild.Fun began with that interest and a personal experiment in vibe coding. I wanted to make a shared city-building world that I would want to return to myself. It is still evolving. Today, you can enter it in your browser, find a city, and explore and build around its terrain.
The real-city terrain catalogue is part of that project. Mountains, coastlines, and rivers shape where a city can grow, and they create some of the most interesting constraints in a building game. We turn public elevation and land-cover data into terrain previews and downloads, with links from each city page to its place in the game. These are processed game maps, not survey-grade source data or a representation of today's roads and buildings.
The work has brought practical puzzles. At a coarse scale, a bridge can look like a strip of land that blocks a river. We tested different ways to find these cases before changing how we classify land and water. Our terrain research note tells that story, including what the current method still cannot promise.
BuildBuild.Fun remains a project made out of a long-standing love of city-building games. You can enter the game or start with a city you know in the terrain catalogue.