I think these were made in Italy in the 70s as decorative items. It originally would have had a tall pointy stopper.
Just remembered: Millers 20th Century Glass, Andy McConnell, page 87 "auto-blown giant decorative bottles/decanters....probably Bormoili, Palma".
I have seen these bottles in a variety of shapes, colours and sizes, for a big collection you would need loads of space!
John.