We need a 3 meter high place to stand on. A 5km long lake. And a 2 meter tall line of lights. And here is why.
How would you show the earth is round? A simple way to do it is to use a lake.
If you had an easy to see object several kilometers away. And you were looking at it from a few meters above the lake. And then you moved down close to the lake surface and the object disappeared. That would show that the earth is actually curved and the curve is blocking out the object.
I can't find a 'show the earth is round art sculpture' anywhere. We would need a location with a long lake view. A height of a few meters that could be moved up and down safely. And a cool looking object that can be seen from kilometers away. Possibly a light buoy anchored out in the lake. or possibly on the other shore. But the main thing is it is easy to see at a distance.
There is a calculator here for how much curvature happens over a particular distance.
You could add Tower viewers and some sort of explainer plaque for the calculations of how much is obscured due to the curvature of the earth would probably be needed. But at least initially most of the difficulty would be making an easy to see object in the distance.
Here are some possible locations
Cormongan Pier