Mahou

Probably the best mainstream lager beer in spain. Comes in two specs: Clasica (green branding, cheaper and worse in cans and bottles but very good if well poured from the tap) and cinco estrellas ("five stars", red-gold branding, full bodied and excellent in cans and bottles). As the URL denotes, fomer competitors Mahou and San Miguel merged some years ago but in my opinion Mahou is still much better than San Miguel (can't tell about the export versions). Very popular in Madrid but you cand find it almost anywhere in Spain.