A voxel-style 3D model of Piața Unirii, the central square of Cluj-Napoca, built with GPT-6 Astra in Codex from one long prompt: St. Michael's Church with its single tall tower, the Matthias Corvinus monument, the Bánffy Palace and Mirror Buildings, over a hundred tiny people (per the author), and a day and golden-hour lighting switch. One of several models' attempts at the same brief on Dan Manastireanu's comparison site; no goal, just a place to orbit.
Piața Unirii is the big central square of Cluj-Napoca in Transylvania, Romania, roughly 220 by 160 metres, dominated by St. Michael's Church and its single 80-metre tower. This page is a small 3D model of it in a voxel style: chunky blocky buildings, tiny blocky people, a lot of terracotta roofs. You orbit it with the mouse or your fingers and it runs in the browser with nothing to install.
It was made by Dan Manastireanu (@danmana on X), a developer whose profile says Cluj, Romania. His post says these were his first experiments with GPT-6 Astra compared with Fable 5.1: the same prompt, given to two models, produced two interactive voxel worlds of the square, and he judged Astra's result good but not quite at Fable's level. The prompt, per the repository, is adapted from a Rome scene prompt by Peter Gostev, with the city swapped for Cluj. This page is the Astra run, made by the Codex agent at its highest effort setting in about 36 minutes according to the run log.
The address it lives at is part of a comparison site: a public GitHub repository where one long scene description was given separately to several coding agents from OpenAI and Anthropic, each making its own self-contained page, plus a viewer that puts two of them side by side. We mirrored only this Astra run, not the site around it.
How to play Piața Unirii, Cluj-Napoca
- The scene opens on a high oblique view from the south, looking across the square: the church with its huge red roof behind the bronze monument, the tower rising from the far side, and orange roofs spreading out in every direction. Drag to orbit, right-drag to pan, scroll to zoom. On a phone one finger orbits and two fingers pan and pinch. We checked all of these; in the code the zoom runs from about 18 metres to 680 metres from the point you are looking at.
- Five keys do the rest, and each has a button in the bar along the bottom. R returns to the opening view. T switches between a clear day at 14:30 and golden hour at 19:15, fading the light over a couple of seconds; at golden hour the sun throws long shadows across the paving and the monument catches a warm glow. V flies the camera down to a walking-height view beside the church and back up again. F starts a slow cinematic orbit that begins near rooftop height and climbs; any drag or scroll cancels it. L turns on eleven floating labels for the church, monument, Bánffy Palace, Mirror Buildings, the former Hotel Continental, the Roman archaeological window, the fountains and five streets. They are off until you press it.
- A small orientation map in the corner shows a wedge for where the camera is pointing. It rotates as you orbit but does not show your panning, and it is hidden on narrow phone screens. There is no sound and nothing to win.
Controls: Drag to orbit, right-drag (or shift-drag) to pan, scroll to zoom. On a phone: one finger orbits, two fingers pan and pinch to zoom. R re-centres on the church and monument, F starts a cinematic flyover, T switches clear day and golden hour, V jumps between street level and aerial, L shows landmark labels. The same actions are buttons along the bottom.
Click Fullscreen above the game for the largest play area. If the game does not load, use Open in new tab to play it directly from our copy.
Why it's worth your time
Up close the church is the best part. The side wall has stepped buttresses topped with small pinnacles, tall pointed windows with a simple tracery pattern, a steep roof that reads as tiles, a polygonal apse at the east end and a clock tower with visible clock faces and a green spire at the north-west end of the nave. It is one tower and one big roof, which is the distinguishing look of the real St. Michael's, and the code's own comments say it deliberately avoids twin towers. Judged against Wikipedia's description (a Gothic church, an 80-metre tower, the Matthias Corvinus monument on the south side), the arrangement matches; we did not measure the proportions.
The monument is a stepped stone plinth, inscribed MATTHIAS REX, carrying a dark bronze rider on horseback, with figures standing around the base. Close up we could clearly see a horse and rider and a couple of standing figures with banner poles; the run's README says there are four accompanying figures. Nearby is a glass-covered opening in the paving with masonry below, standing for the Roman Napoca excavation, and at the south end a row of shallow pools with small water jets.
The square's edges are lined with continuous rows of several-storey buildings in cream, ochre, pink and grey plaster with arched ground floors, and at the east end of the square two matching corner buildings with green domed corners frame Strada Iuliu Maniu, which is how the real Mirror Buildings are described. These are stylised interpretations, not portraits: the README calls it "a voxel architectural interpretation with approximate geographic proportions, rather than a surveyed digital twin", and we agree.
The square is populated: small blocky people walking, sitting on benches and cycling, café umbrellas, small flocks of pigeons, and a handful of boxy cars, a yellow taxi and a teal bus on the streets around it. The README counts 116 people and 12 vehicles; we did not count them.
What works less well is the wider city. Zoom out and the neighbourhood turns into regular rows of similar red-roofed houses, and the distant "hills" are stepped green bands with tiny houses that look like terraces from a high camera. That is fine for a backdrop but does not read as Cluj. The landmark labels also do not hide behind buildings: a label can float over the church roof when the thing it names is on the far side, and at the opening angle the Hotel Continental label overlaps the page title.
It is light and fast. The whole page is about 0.5 MB, with Three.js bundled into a single script, and makes no network requests. In a normal Chromium window on a laptop it held 60 frames per second in both lighting modes. The on-screen frame counter is at the bottom right. The GitHub repository has no licence file for the page's own code, so reuse is not spelled out, and the bundled Three.js carries its own MIT licence. This entry was found through Tripo's GPT-6 Astra prompt collection; the creator's own post, quoted above, is the primary source.
How it was made and where it lives
Hosted on Vercel. The author publishes as danmana. Original: https://piata-unirii.vercel.app/runs/gpt-astra-xhigh-01/. The Play button above runs our own unmodified copy, so the game keeps working here if that page goes down — which on free hosting usually has nothing to do with the author. Nothing about the game itself is changed, and the original stays linked from every page.
The post that led us here
Dan Manastireanu@danmanaFirst experiments with Astra compared with Fable 5.1. Initial results look good, but not quite Fable level. Same prompt, two interactive voxel worlds of Piața Unirii in Cluj-Napoca.
If you like Piața Unirii, Cluj-Napoca, try these
For another explorable model of a real place, try Tokyo DisneySea, a stylised 3D map of a theme park with named attractions, or City Atlas, a generated city you can orbit and re-roll.
Frequently asked questions
- Is this a game?
- No. There is no goal, score or enemy. It is a model of a place to orbit, fly over and switch between day and golden hour.
- Who made it, and with what?
- Dan Manastireanu (@danmana). Per his post, the page is the GPT-6 Astra result of a prompt he adapted from Peter Gostev's Rome scene; the run log lists Codex, GPT-Astra and xhigh effort, and about 36 minutes of working time. The repository says its runs are generated, not hand-written.
- Why is the address /runs/gpt-astra-xhigh-01/?
- Because it is one of several runs on a comparison site. Each run is a different agent's attempt at the same voxel Piața Unirii brief, and the site includes a viewer for putting two side by side. Only the Astra run is mirrored here.
- How accurate is it?
- Recognisable rather than exact. The church with a single tower and big roof, the monument to its south, the Bánffy Palace on the east side and the Mirror Buildings at Iuliu Maniu match the real square's layout as Wikipedia describes it, but facade details are invented and the outer city is generic. The author calls it an interpretation, not a survey.
- Does it work on a phone?
- Yes, in our emulated-iPhone test. One finger orbits, two fingers pan and pinch to zoom, and the bottom buttons do what the keys do. We did not try a real handset, so performance on a phone is unknown.
- Does it need the internet?
- Not from us. The page, its code and Three.js are all served from this site with no outside requests, and the page needs a browser with WebGL 2.
- Is Piața Unirii, Cluj-Napoca free to play?
- Yes. Everything on Floating Arcade is free, with no account, ads or downloads.
- Can I embed this game on my own website?
- Yes — copy the snippet below. The embedded player links back here, which is how we ask to be credited.
Embed Piața Unirii, Cluj-Napoca on your site
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