Kvarken Archipelago

The narrow throat of the Gulf of Bothnia, eighty kilometres from the Swedish mainland to the Finnish but only twenty-five between the outermost islands, and just twenty-five metres deep. The land here is rising at almost ten millimetres a year, one of the fastest rates anywhere. On the Finnish side the archipelago runs to over 5,600 islands beyond Replot and Björkö. When the sea froze solid, mail was carried across on the ice from Sweden to Finland. The first successful swim across took three men twelve hours and two minutes, on 24 July 2018.