Porto, Portugal, Unesco Heritage Site, old city houses and Douro river during sunrise, blue hour with 3 birds flying by

oporto porto douro ribeira douro river rio douro panoramic dom luis i bridge panorama portugal blue hour river portuguese sunrise bridge town world heritage site cityscape city riverbank skyline sky unesco european europe travel tourism urban cloudy sky embankment building downtown architecture destination dom old clouds sky architectural landmark tourist day water colorful luis historical historic traditional attraction outdoor