In 1640, Helsingfors was moved south from its original location at the mouth of the river Vantaa (in Swedish: "Vanda"), but the improved harbour failed to attract traders. The plague of 1710 killed the greater part of the inhabitants of Helsingfors. After Russia began to assert itself in the Baltic with the foundation of St. Petersburg, Helsingfors was fortified by the Swedish authorities to protect the city from Russian attacks. Construction of the island fortress Sveaborg (in Finnish: "Viapori", today: "Suomenlinna") began in 1748.