Around here, they say "God created the earth and man the Douro", and to see the river's banks sculpted into steep terraces supporting row upon row of vines is to understand the immense amount of manual labour lavished on this landscape over 20 centuries. Between mid-September and mid-October visitors can witness the extraordinary spectacle of the harvest, as thousands of grape pickers swarm the terraces, which cover over 40 000ha dedicated to the production of grapes for Port.