The Monastery of Serra do Pilar sits on the hilltop in Gaia directly above the Ponte Dom Luís I, and its round church and circular cloister are among the most unusual architectural forms in Portugal. Built in the sixteenth and seventeenth centuries, the monastery belongs to a rare tradition of circular ecclesiastical buildings; the church has a rotunda plan with a Renaissance dome, and the cloister wraps around it in a complete circle. Both are designated UNESCO World Heritage Sites as part of the Historic Centre of Porto inscription.
The hilltop location is at least as important as the building itself. From the terrace in front of the church — now one of the classic viewpoints in Porto and Gaia — you can see the entire sweep of both cities from the Atlantic coast to the upstream Douro gorge. The famous image of Porto's tiled façades stacked above the Ribeira waterfront is best seen from precisely this spot at golden hour. The Jardim do Morro gardens are immediately adjacent.
The monastery interior, including the cloister and the church, can be visited during specified opening hours. The terrace is accessible at any time and is free.