Flat terracotta tiles on a roof, with some age, lots of lichen and moss. Theoretically you should clean off the growth to keep your roof in good condition, but hardly anybody bothers. Note the lack of gutter, which is traditional for here. Gutters are rather a modern affectation, and the old buildings can suffer if the soil around them dries up due to water off the roof being collected and piped away rather than being allowed to fall on the ground about half a metre beyond the walls.
A nice smart slate roof on a tower peeps out above other long low roofs of slate or flat terracotta tile. The tower roof is finished with 'zinc' (actually pewter type alloy or galvanised steel). There is a decorative pattern in the slates (usually created by hanging the slates on a different alignment) and a monogram on the chimney of forged iron.
Another flat terracotta tile roof (with a bit less lichen and moss). On the right is a special curved tile with is for ventilation.