Identify this movie with a very special kind of guillotine tobogan

I only remember one thing very clearly about the movie so I think it's going to be very hard to find.

The movie was taking place a long time ago: maybe featuring vikings or romans (I know that is not precise at all).

What I remember clearly is this: there were people that had been captured by a clan or a tribe and they were being killed by a very special method: the man was pushed in a gigantic tobogan and gaining a lot speed (the tobogan was very steep and very long) and, at the end of the tobogan, there was a huge blade that was cutting the man in two.

It was cutting them in two from the head to the groin, leaving two symmetrical part of the body.

I'm pretty sure there were a lot of spectators enjoying the "show" of the ennemies being cut in two parts.

I'd say the movie is at least 30 years old.

I saw this as a kid and this movie, that part of the movie, totally freaked me out...