Castelnuovo di Porto lies on a tufa ridge, between the Chiarano and Mola valleys, a short distance from Rome. It is included in the Veio Regional Park, established in 1997 to protect what remains of the biodiversity in areas deeply transformed by man. The Rocca Colonna, at the highest point, dominates the landscape. The first fortification, which took place before the year 1000, was built by the Roman prince and senator Alberico. Over the centuries, the borgo has developed in a typical medieval layout around the castle. Once surrounded by agricultural villas and tufa quarries, Castelnuovo probably resembled the village depicted in the 15th century fresco in the small Church of San Sebastiano. The Colonna family gained possession of the borgo in the 15th century and fortified the perimeter with massive walls and circular turrets. Alessandro and Sciarra Colonna transformed the fortified fortress into a Renaissance palace. Inside the city walls is the Collegiate Church of Santa Maria Assunta with its 13th century bell tower. It was rebuilt in Baroque style in 1753-56 and preserves the Triptych of the Saviour of 1501, attributed to the school of Antoniazzo Romano.