In the territory of Castrocielo there is a small stretch of water formed by the Capo d’Acqua spring, which in ancient times fed a system of lakes (now dried up) known as ‘Forme d’Aquino’, which were placed in defence of the Roman city of Aquinum. In 2017, the entire area was declared a Natural Monument of the Lazio Region, consisting of two distinct areas: the monumental remains of the Roman city (129 hectares) and the Capo d’Acqua spring wetland (3 hectares).

Near the lake is the small Church of the Madonna del Pianto (also known as the Church of Our Lady of Seven Sorrows), in Romanesque style, originally with a single nave. In the 18th century, the single lancet windows were closed and three Baroque altars were inserted. One enters the church through a pronaos with round arches. On the entrance portal is a lunette, originally painted, with two small square limestone windows, closed by iron grilles. During the Second World War, the frescoes were severely damaged. In the 1970s, the fresco of the Crucifixion on the high altar was removed for restoration in the Vatican Museums in Rome.