Lake Seewen was created by a rock fall in prehistoric times and has long since disappeared. Hence the name «Sewin», which means «by the lake». Attempts in the 16th century to drain the lake by digging an over 200 m long drainage tunnel through the earth and rock mass were met with modest success. The runoff was too high, resulting in a swamp landscape. It was not until 1923 that the former lake basin was turned into cultivated land after an extensive melioration process. The lake basin can still become waterlogged after strong rainfall, which makes it easy to visualize the prehistoric landscape.

Seewen has belonged to canton Solothurn since 1458. The handsome parish church of St. German with its two Baroque towers dominates the village. Besides the enchanting landscape, Seewen is famous for its Museum of Music Automatons. Heinrich Weiss, a passionate collector of mechanical instruments of all kinds, bequeathed his entire collection – one of the world's largest – to the Swiss Confederation in 1990, under the condition that the future exhibition remained in Seewen.

The village also has a rather sad claim to fame: as the place where one of the worst, hitherto unsolved violent crimes in Swiss history was committed. At Whitsuntide 1976, five people were shot dead in a weekend home. The murder weapon wasn't found until 20 years later, and the suspect was never caught.