Sermoneta is in the hills overlooking the Pontine Marshes in the Lepini Mountains, 257 metres above sea level with wonderful views. It is a small town (population of 7480) with a castle, a cathedral and a surrounding wall. Its houses are mainly mediaeval. The Annibaldi built the town in the 12th century. In 1798 the French invaded the town taking with them 30 cannons from the castle.
This is the campanile (bell tower) of the cathedral Santa Maria Assunta. It was built in the 13th century on top of an ancient Roman temple of Cibeles. I have heard a choir singing inside the church - which was lovely.
The castle Caetani in Sermoneta can be visited. There is a fort with a bridge and its prison can be visited too. There is also a museum of ceramics inside the castle. Well worth a visit.