It's a tram/light rail project meant to connect a large island in Eastern Helsinki with downtown. The most significant part are 3 new bridges that only carry trams, cyclists and pedestrians.
The tram will start operation in 2027, but the bridges are opened for pedestrian traffic as they are completed. The next one should be finished later this summer.
Here's a short video of the project: https://www.youtube.com/watch?v=KTW2VIf5k0I