The massive Parco Naturale Regionale di Bracciano Martignano, surrounding the Lago di Bracciano (lake) northwest of Rome, has a good variety of running opportunities for those visiting Anguillara Sabazia, Bracciano, Vicarello, Trevignano Romano, or any of the other surrounding cities. There is a road alongside the lake, but it’s busy and lacks a sidewalk or shoulder.
The best running options are the scenic roads passing through the farmland east of the lake. Via di Monterosi (3.5 km one-way) and Lago di Martignano (4.6 km one-way) are both particularly scenic options. Note: quite hilly.
There is also an 8 km bike route (mostly gravel) departing from Mola Vecchia dell’Arrone in Anguillara Sabazia.