Syntenic regions are calculated from pairwise (between two species) whole genome alignments. In the 'Location' tab, click on the 'Synteny' link in the left hand menu available under 'Comparative Genomics' to view conserved blocks of sequences. See an example here from Ensembl Plants for syntenic regions between rice and maize. Synteny data can also been viewed in the 'Region overview' panel in the 'Location' tab. Click on 'Region overview' in the left hand menu, click on 'Configure this page' then on 'Synteny' and choose the species. See an example here from Ensembl Plants for syntenic regions between rice and three other species.