Behind the game

How Strata rebuilds a city

Nothing in a Strata diorama is drawn by hand. Every puzzle is a real city reconstructed from public geographic data — the same elevation, climate, water, street, and building records that mapmakers and earth scientists use — then rendered as an interactive 3D model in your browser.

One diorama, five layers of data

The game starts with everything stripped away except the land itself, and each wrong guess restores one layer: weather, then water, then roads, then buildings. That order is deliberate — it runs from the hardest clue to the easiest. Bare terrain asks you to recognize a landform; a skyline practically hands you the answer. Each layer below is built from a different real-world dataset.

Terrain: reading the land

The ground is built from global elevation tiles hosted on AWS Open Data — raster tiles that encode the height of every point on Earth, assembled from surveys such as NASA's SRTM radar mission. Strata samples those heights across the city's footprint and raises a 3D mesh from them, so the hills of San Francisco, the bowl of a valley city, or the dead-flat spread of a prairie town are the genuine article. For most puzzles this first layer is the whole game: river bends, coastal shelves, and ridgelines are more distinctive than most players expect.

Weather: the climate stamp

The weather layer comes from the Koppen-Geiger climate classification — the standard system geographers use to label climates, in its modern 1 km form covering 1991 to 2020. It cannot name a city, but it can eliminate most of a hemisphere: a humid subtropical stamp rules out the Mediterranean, a cold continental one rules out the tropics.

Water: rivers, lakes, and coastline

Coastlines, rivers, and lakes come from OpenStreetMap. Water is often the single most recognizable feature of a city — the S-curve of the Thames, Manhattan surrounded on all sides, Chicago pressed against a wall of lake. When the water layer arrives, a puzzle that felt impossible often collapses into two or three candidates.

Roads: the street grid

The street network is also OpenStreetMap data, rendered as a texture over the terrain. Street patterns are fingerprints: a rigid grid says North America, a tangle of medieval lanes says old Europe, broad ring roads say a planned capital. Highways radiating toward the edges hint at what the city is connected to.

Buildings: the skyline

The final layer raises the buildings — real footprints and heights from OpenStreetMap, not a generic skyline. Density clusters where the real downtown is, towers rise where they actually stand, and low neighborhoods stay low. If you have ever tried to guess a city by its skyline, this layer is that puzzle in miniature.

The strata underneath

The game's name comes from the diorama's side profile: the block of earth under the city shows real geological layers from Macrostrat, a research database of the rock columns beneath North America and beyond. The sandstone, shale, or granite under a city is not a clue you need to win — but it is real, and it is why the diorama looks like a slice cut out of the planet.

From data to 3D in your browser

Each city is baked ahead of time into a compact set of assets — a height field for the terrain mesh plus image layers for land cover, water, streets, and buildings — so your browser downloads a few small files instead of querying live map services. The 3D scene itself is rendered with three.js and runs on phones as well as desktops, with no download or sign-up.

Sources

• Terrain tiles (Terrarium) on AWS Open Data — Global elevation raster tiles assembled from sources such as NASA SRTM and USGS 3DEP.
• Koppen-Geiger climate maps (Beck et al., 1991-2020) — 1 km present-day climate classification used for the weather layer.
• OpenStreetMap — Coastlines, rivers and lakes, the street network, and building footprints and heights.
• Macrostrat — Geological column data behind the rock strata in the diorama's side profile.

Try reading a city yourself

The best way to understand the pipeline is to play it: start from bare terrain and see how far you get before the skyline gives it away. There is one new city every day, in a US + Canada mode and a Worldwide mode.