@Emerfirek Are there well-known pyramids in places other than Egypt and Central America? If somewhat claimed so, I might be somewhat likely to believe a lost South Asian jungle city might have had pyramids, but other places are less likely. Middle East would have had ziggurats if you counted them as pyramids. but they aren't quite the same.
@Kaarme
Though, if you think of a pyramid as just a geometric form, regardless of size, it's pretty simple for anyone to make one. I'm also assuming there's actual sand at the sand dunes, but toy pyramid molds for making sand castles do exist. Doesn't really seem weird or unusual to me.