Something has been standing on this rock since 1815 — first unilluminated daymarks, shapes painted and raised purely to be recognised in daylight, then early lighthouses. A navigator coming up from the Baltic in the years before the present tower had to identify the skerry by silhouette alone, and hope the weather held long enough to do it. One of those earlier beacons survives in a drawing made for *Finland framställdt i teckningar*, the illustrated survey of the country published between 1845 and 1852, back when the island's name was still written in older forms that have since fallen out of use.

The present tower went up in 1863: brick and mortar over a granite base, octagonal in plan, five storeys, rising 21 metres with its light 34.2 metres above the sea. The paintwork is a red tower over a base left the colour of the stone. What made it genuinely unusual was not the height but the calendar. Russarö was the first lighthouse in Finland to operate through the winter months as well as the summer, which sounds technical until you remember why Hanko exists at all. The port was built because the sea here freezes last, and a winter port is worth nothing without a winter light. Somebody had to live out on the rock and keep it burning through the dark half of the year. The keepers finally came off in 1949, when the light was automated.

By the 1930s the island carried Finnish coastal artillery — heavy 234-millimetre guns sited to command the approaches. On 1 December 1939, the second day of the Winter War, the Soviet light cruiser *Kirov* came south of Hanko with the destroyers *Stremitelny* and *Smetlivy* and engaged the battery. The exchange did not last long. The Soviet ships broke off and withdrew, and *Kirov* went back to base carrying seventeen dead and thirty wounded — men who had been at war for roughly thirty-six hours. Ashore, the gunners kept their guns. The lighthouse, standing among the batteries, survived a naval action fought at the range its own beam was designed to cover.

Russarö remained a military island and remains one. That closure has had one civilian by-product: the Finnish Meteorological Institute's weather station here has been recording an exposed, unshadowed patch of the outer Baltic for decades, and the numbers describe a place with a genuinely maritime temperament. The 1991–2020 records run from −33.6°C at the coldest to 30.5°C at the warmest — a wide span in absolute terms, but far narrower than what the mainland a few dozen kilometres north endures, because open water is slow to warm and slow to let go.

In summer, day cruises run out to Russarö from Hanko's Eastern Harbour, and passengers can walk a little of the island. What they cannot do is climb the tower. The interior has deteriorated badly enough that entry is no longer permitted, so the Eye of Hanko is now something to be looked at rather than looked out of — a working navigational aid that has quietly become a monument to itself. From the deck of the boat you get the view that matters anyway: a low grey skerry with a red column on it, the Baltic running away south with nothing in the way until Estonia, and the light doing what it has done since 1863.