Grottaferrata still has its abbey, founded in the 11C by Greek monks. The church in the second courtyard, Chiesa di Santa Maria has a fine 12C Romanesque bell tower. The interior reveals a triumphal arch adorned with a large Byzantine mosaic (late 12C) depicting the apostles at Whitsun. The chapel in the right nave, Cappella Farnese, is decorated with frescoes (1610) by Domenichino illustrating the life of St Nil.