aerial view of a triangle ravelin or demi lune with a redoubt in the ditch between 2 bastions in almeida portugal

almeida architectonic architecture bartisan bartizan blue bridge building cannons castle citadel city cityscape ciudadela counterguard counterscarp covered daytime ditch door draw edification edifice entrance exterior facade famous flanking fort fortification glacis guerite hornwork lunette military moat portugal pyrenees rampart ravelin redoubt sentry box sightseeing sky star shape shaped stone tenaille acopy chauguette