Where are these 3 white flagstaffs in front of a commemorative stone, river and valleys? [closed]

I cut out my sibling's head from this picture. Sibling thinks this was in North America but can't remember. Perhaps Europe? Anyone recognize this?

We see a plaque with text on a stone like a commemoration? We see a boat cruising. We can't figure out what those black beams rods are behind the three white poles and people are sitting on the shore line.