Riddarfjärden is a bay of lake Mälaren in central Stockholm. Stockholm was built in 1250 on an island in the stream where lake Mälaren (from the west) drains into the Baltic Sea (to the east). The island is today called Stadsholmen and constitutes Stockholm's Old Town. It is surrounded by land to the north (Norrmalm[?]) and south (Södermalm[?]), and by water to the west (Riddarfjärden) and to the east (Strömmen).