At Þvottá in Álftafjörður are important remains associated with the Christianisation of Iceland. According to tradition, the missionary Þangbrandur stayed with Síðu-Hallur around the year 1000. A protected ruin stands near Þangbrandsbrunnur, and Þvottá later became a church site.
Merkar minjar við Þvottá sem tengjast einu þekktasta skeiði Íslandssögunnar.