The churches of St Martin (near the Roselli district), St Mary of the Limata (near the Plauto district) – both documented in the 11th century – and St Erasmus (whose location is uncertain), for which records date back to the 12th century; and excluding the Monastery of St Angelo di Pesco Mascolino (11th century) – which, moreover, has fallen into ruin and lies within the territory of Casalattico (Casale) – the church of S. Pietro in Campomayno is the oldest church still standing in the Casalvieri area, having been first mentioned in records dating back to 1248.
The very first parish church of Casalvieri – which still stands, albeit deconsecrated – that of St Nicholas, is, according to some scholars, from the 11th century (though this is by no means certain); it is first documented only from the early decades of the 14th century.
The Church of Saints John the Baptist and John the Evangelist, now the parish church, was first built in the 16th century and then rebuilt in its present form during the 18th century, whilst the Church of Santa Maria delle Rose in Roselli dates from the 17th century.
The date 1248, relating to the existence of the church of St Peter, is that of a papal bull issued by Innocent IV, by which the church and its many estates were assigned to “Maestro“ Adenolfo di Arpino, a canon of the church of Santa Maria di Castro Scipione, which was situated in the area now known as Fontana Liri.
The name “S. Pietro in Campomayno” (i.e. Campomagno = Campogrande) derived from the presence of vast and fertile agricultural land in the vicinity – still visible today – belonging to the church and situated on the border, even now, between the municipalities of Casalvieri and Arpino.