A student of mine used google translator to translate the Portuguese "miradouro" into English. Instead of an expected viewpoint, scenic overlook or similar, the translator suggested "belvedere". She has asked me the meaning of belvedere and I have been unable to find it in my two dictionaries (Longman and Oxford). So, what is 'belvedere' in English?
A "belvedere" is a structure which commands a scenic view, not the view itself. The word itself comes from the Italian for "beautiful view", but its English sense is limited to buildings and the like.
: a structure (as a cupola or a summerhouse) designed to command a view
This M.C. Escher drawing entitled "Belvedere" is what comes to my mind when I think of the word:
Belvedere - A roofed structure, especially a small pavilion or tower on top of a building, situated so as to command a wide view.
It seems as though this may actually be a more accurate translation than "viewpoint". However, it depends on the definition of "miradouro". If a "muradouro" is typically a viewpoint with a roofed overhang situated on a building, then a "belvedere" could be exactly what you're looking for.
If not, then it could be a percularity in translation. I suggest comparing definitions of miradouro (in Spanish) and belvedere to see how accurately the two compare.
Per wiktionary, a belvedere is “A turret or other raised structure offering a pleasant view of the surrounding area”. An example of its use:
The most important thing, she reflected, as she stood on the balcony of the Mairie which formed a most useful belvedere over the town, was to make her appearance as commonplace and down at heel as possible [...] (1919, Ronald Firbank, Valmouth, Duckworth, hardback edition, p. 57)