The patron saint of Rivello is Saint Nicholas of Bari, celebrated on 6 December. Since the Middle Ages the town was divided into two distinct quarters: the upper one, whose inhabitants, called bardàv'ti, were tied to the Latin-rite church of San Nicola di Bari, and the lower one, whose inhabitants, the bardàsci, followed the Greek-rite parish of Santa Maria del Poggio; the town's place names still preserve the memory of the two ethnic groups that gave rise to the town, the Lombards and the Greeks, in the names "Fonte dei Lombardi" and "Piazza dei Greci".
The parish church of San Nicola di Bari, of medieval origin, was enlarged and raised in the first half of the 18th century, partly over the ruins of the old castle; the façade, embellished by an 18th-century staircase in local stone, leads into an interior with 18th-century paintings, including a Madonna of the Rosary by Paolo de Matteis from around 1715-18. Below the church lies the crypt of San Nicola, with its distinctive cross vaults on columns of local stone, second in size only to that of the basilica of San Nicola in Bari: both the church and the crypt were sacked by Napoleon's soldiers passing through during the siege of Lauria in August 1806, when horses were even stabled in the crypt.
