Complex sentence: Sääksmäki's most famous building is of the medieval stone Sääksmäki Church, which was built at the end of the 15th century and is one of the oldest buildings in Finland.
Split into simpler sentences: Sääksmäki's most famous building is the medieval stone Sääksmäki Church, built at the end of the 15th century. It is one of the oldest buildings in Finland.