The 18th-century Torreón de Igeldo (Igeldo Tower), originally a lighthouse and currently a panoramic viewpoint, presides over Mount Igeldo, which is a fun place thanks to its neat attractions park.
I recommend you ride up the mountain on the funicular railway, the oldest in Euskadi and in operation since 1912, to observe and photograph the city from a spectacular vantage-point.
A prominent landmark on the mountain is the lighthouse on its west side, built in 1855 by civil engineer Manuel Peironcely; it's the perfect place to enjoy the beauty of the sea and the Igueldo cliffs.