Jutting up from the crest of a flat-topped hill, the Callanish Standing Stones comprise one of the world’s best-preserved Neolithic monuments. Erected 5,000 years ago, they predate England’s famous Stonehenge and are believed to have been an important place for ritual activity for at least 2,000 years. To this day, archaeologists disagree about why the stones were placed here, but the general consensus is that the cross-shaped arrangement served as a kind of astronomical observatory. Unlike at Stonehenge, visitors to Callanish can walk right up to the monoliths, which are more roughly hewn than their English counterparts. There’s also an interpretation center and café on-site; it’s closed on Sunday, but the stones are always accessible.