CityGems
Light modules that clip onto the lampposts, railings and fences a city already has — no digging, no foundations, no new poles.
At a glance
- Module size
- Weatherproof unit within a 40 cm bounding cube
- Mounting
- Clamps to existing poles, railings and mesh fences, 1–1.5 m above ground. No groundwork
- Face
- 32×16 LED matrix behind a 3D-printed diffuser — it can say RACE or count you down, so no sign is needed to explain it
- Sensing
- Time-of-flight distance plus passive motion radar. No cameras
- Networking
- Device-to-device radio, so a line of modules becomes one timed run with splits
- Maintenance
- Each module reports its own status; faults are found without a patrol
- Audience
- Designed around 12–35 year olds
Who it is for
- Cities that want activity in overlooked corners without building anything new
- Sport organisations running routes, challenges or neighbourhood programmes
- Sites where digging, foundations or new poles are not on the table
- Anyone who needs more than one of something, in more than one place
What you can play
Wake Me Up
Move close, and it plays with light and music.
Start a Race
Step closer to begin a speed race between the gems.
Unlock a Secret
Stay close for a few seconds to find a hidden game.
All three are printed on the how-to-play sign next to the module, so nobody has to be told what to do. Race times go to an online leaderboard.
Where it fits
Running and cycling routes
A line of modules becomes a timed course with splits at every point along it.
Sports courts and cages
Clamps straight onto the perimeter mesh — reaction games and drills at the fence.
Underused paths and cut-throughs
Light and response where a place currently reads as somewhere not to linger.
Parks and campuses
A trail people follow between points rather than one object they stand at.
Where it is the wrong call. A single hero object at a landmark site. One CityGem on its own is a light on a pole; the value is in a network of them. If you want one memorable thing in one place, that is a Wave-shaped problem, not a CityGems-shaped one.
The whole point: it goes on what is already there
Most public-space installations start with groundwork. A foundation, a new pole, a cable trench, a permit for all three, and a bill that is mostly civil engineering before a single light turns on.
CityGems start from the opposite end. Every module clamps onto something a city has already paid for and already maintains — a lamppost, a handrail, a bollard, the mesh fence around a sports court. No digging, no concrete, no new street furniture, and nothing that cannot be taken off again without a trace.
That is the difference between a project that needs a capital works budget and one that needs an afternoon.
Each unit sits within a 40 cm bounding cube and mounts 1–1.5 m above the ground, which is roughly where a hand goes without anyone having to think about it.
What you do with it
You put a hand near it and it answers immediately. That is the whole interaction — no app to download first, no instructions to read, no account. Everything else is built on top of that one moment working.
Three ways in, printed on the sign next to it:
- Wake Me Up — move close, and it plays with light and music
- Start a Race — step closer to begin a speed race between the gems
- Unlock a Secret — stay close for a few seconds to find a hidden game
Because the face is a real LED matrix rather than a colour wash, the module can
say RACE or count you down itself, so nobody needs a sign to explain what is
happening. Race times go to an online leaderboard, so a run means something
after you have finished it.
The modules talk to each other over device-to-device radio, which is what turns a line of them along a route into a single timed run with splits at every point — rather than a row of unrelated lights.
What makes it hard
You do not own the thing you are mounting to. A lamppost belongs to the city, carries its own cabling, and has to stay serviceable. Anything attached has to be non-invasive, safe, and acceptable to the people who maintain the street — which made the clamp design matter as much as the electronics.
Every unit is somewhere inconvenient. One module on a bench is easy. Two hundred across a city means anything requiring a visit — a reset, a battery, a firmware update by cable — does not scale. Each module reports its own status, so maintenance is driven by data rather than by patrol.
It has to read as intentional. A street is visually noisy: bikes, bins, signage, graffiti, greenery. An object that looks like utility hardware either disappears into that clutter or reads as something to vandalise. The faceted shape is doing a job — it catches light in daylight, when the LEDs are off and the thing still has to look like it belongs.
Getting the object right
The form went through physical shape tests before any electronics were involved, working out how a faceted surface catches and scatters light.
The production diffuser is 3D-printed. That keeps the facets crisp, and it lets the wall thickness vary across the face so the LED matrix behind it reads as even light instead of a grid of dots.
Behind that face is a 32×16 LED matrix, which is enough to show words, numbers and animation rather than just colour.
Sensing is a time-of-flight distance sensor plus passive motion radar. No cameras, same as everything else we build for public space.
On the street, at night
Early enclosures went straight onto Rotterdam lampposts — not to test the electronics, but to see how the object reads at street scale against real background clutter, and whether the mounting is honestly practical.
Most of the testing happens after dark, because that is when a light installation does its job.
Brightness is measured rather than eyeballed. A module has to be clearly visible from a distance without dazzling anyone walking past it, and without adding to light pollution in a residential street — a real constraint for something mounted at eye level.
Concept placements along Schuttersveld were used to settle spacing, colour variety, and how the gems hold their own against graffiti and greenery at a scale that does not exist yet.
Built with THUAS
The LED and sensor core was prototyped with The Hague University of Applied Sciences, which gave students hands-on work building the interactive heart of the modules — and gave the project a second set of eyes on the electronics.
Where it stands
Working modules are mounted and running on real street furniture in Rotterdam, with a printed how-to-play sign and an online leaderboard, in front of people who did not know they were coming.
Sportbedrijf Rotterdam has shown strong early interest, and the city’s planners have affirmed the approach of mounting to infrastructure that is already there.
What comes next is a pilot at real scale: a route or a site with enough modules to test the networked behaviour — timed runs, splits, fleet reporting — rather than the single-module interaction, which is proven.
If you have a route, a park, a court or a campus in mind, that is the conversation to have.