The Roman rotunda of St. John the Baptist is one of
the oldest churches in Slovenia. It is smaller in size, and was built as a
subsidiary church in the 11th century. It was used as a baptistery and was then
located at the easternmost part of the Lavantine pre-parish.
The church is a representative of Roman rotundas,
which have now become rare in Slovenia. A three-sided presbytery was added to
the round building between the end of the 13th century and the early 14th
century. The interior of the presbytery is adorned with murals, representing
the most important part of the church's cultural heritage.