UFO Secret Report

What is the name of the oldest ancient alien ruins found in South America?

I was previously watching a TV show on the History Channel called “Ancient Aliens.” The show had a sections where it talked about an interlocking wall made of granite and direite, the second hardest rock on earth next to diamond.. This wall was considered to be made by an indian tribe, but the stones were hundreds of thousands of pounds, and in order to cut these stones, they had to have used diamond tipped blades. Also, the lines cut into the stones were perfectly straight and the width and depth throughout the entire cut were almost exactly the same. Experts say that today making this type of wall is close to impossible. Please help me out if you know the name of the ruins/wall. I believe it is Belize but I am not sure.
I’m not saying for fact that it was done by aliens, but that is what many expert suggest, because they all agree that they had to have created plans in order to build the project, and that means they had to have had a writing system, and the indian tribe that was given the credit for the build had no writing system at all. I just want to know the name of it so I can look into it more myself. And I don’t even know what SG-1 is…sorry. lol