"The history of this church dates back to the 5th century when a wooden church was built, maybe on the foundation wall of a abandoned Roman building. A first stone church of the 8th or 9th century was replaced by a newer building around 1000, and in the 12th century a church in Romanesque style was built but stayed unfinished. Finally the earthquake of 1356 demolished substantial parts of the church.
"After 1359 the church was repaired and completed. In 1420 it was enclosed with a seven meters high curtain wall with battlements and two gate towers to serve the residents of the village as a refuge in times of danger, since the old castles on the nearby Wartenberg were also partially destroyed in the earthquake.
"The charnel chapel was built in the 2nd half of the 15th century at the inside of the southern wall. It is a two storey building with a lateral external staircase to the upper floor. In 1513 the building was provided with paintings on the facade and the interior; they were painted over after the Reformation and were rediscovered during renovation work in the 20th century. (Link 3.)
Link 2: https://en.wikipedia.org/wiki/Fortified_Church_of_St._Arbogast
Link 3: http://www.waymarking.com/waymarks/WMJH9Y_Beinhaus_at_St_Arbogast_Muttenz_BL_Switzerland