I think e I don't think non vengono mai usati da soli, ma vengono sempre seguiti da so, come nell'esempio, o da una proposizione come nel caso di I think/I don't think he went to the concert.
This is a prehistoric stone structure in the form of a flat-topped cone that is peculiar to Sardinia, which contains about 8,000 of them. The earliest examples date back more than 5,000 years B.C. They are variously thought to have been fortresses, look-out towers, parliaments, or residences of tribal chiefs.