[1] The village is located in a nearly 3 km-wide lowland of the Aare in the west of Solothurn's part of the Swiss Plateau.

[5] The Selzach train station on the Solothurn-Biel line is approximately 1 km from the village center.

[9] At around 1260, the Neuenburg-Strassberg noble family established the medieval town of Altreu, which was fortified with walls, trenches, and a castle; a wooden bridge over the Aare was also constructed at that time.

[9] The region north of the Aare which separated from the Strassberg Herrschaft in 1309 was named after Altreu; this area included the municipalities of Selzach and Bettlach, as well as the western part of Lommiswil.

[9] A hamlet grew in the location of the former town which, though part of the Selzach municipality, possessed a degree of autonomy until 1831 with its own Ammann (bailiff), common land, and Weibel (a type of Swiss official with various administrative and ceremonial duties).