The Piscina Mirabilis was a freshwater cistern on the Bacoli cliff at the western end of the Gulf of Naples. One of the largest freshwater cisterns built by the ancient Romans, it was situated there in order to provide the Roman western imperial fleet at Portus Julius with drinking water.
The cistern was dug entirely out of the tuff cliff face and was 15 metres high, 72 metres long, and 25 metres wide. It was supported by vaulted ceilings and a total of 48 pillars. It was supplied with water from the main Roman aqueduct, the Aqua Augusta, which brought water from sources in Serino near Avellino, 100 kilometres distant, to Naples.
The ancient cistern is currently in private hands, but parts of it may still be visited by the public.
References:Towering 52 meters above the sea, Bengtskär lighthouse is the tallest one in Scandinavia. The building started in in 1905 after the shipwreck of S/S Helsingfors and was completed in 1906. The lighthouse was designed by architect Florentin Granholm. On December a special petrol lantern, designed and built in Paris, was brought to Bengtskär and installed atop the tower.
German fleet bombarded Bengstkär in the First World War in 1914. Since the Gulf of Finland was heavily mined, it was not until 1919 that the surrounding seas were declared safe for shipping, that the light was lit again.
After the war the military value of Bengtskär increased as part of the defence system of independent Finland. In Second World War (1941) Soviet Union made a suprise attack to island. After a bloody battle, the small Finnish garrison emerged victorious. Intermittent repairs to the facility continued during the post-war period.