It is, indeed, Excalibur. I went there every year when I lived in Minnesota. And every time I went, without fail, the Excalibur would get stuck at least once. I guess the tow chain didn't go up as high as it should or something, but it was very unreliable from what I remember.
But it was one EXTREMELY fun amusement park
If you look towards the top left corner, you can also see one of the stations for a train they had surrounding the park submerged, as well as some track. The big building in the top right hand corner is, I think, one of those 360 degree movie theaters (forget the name off the top of my head). The white slides are part of the waterpark portion of Valleyfair.