You can find this route on the BikeSquare app with code E05
The itinerary starts in Grottaferrata, you will go through Rocca di Papa's wood. Going up you can see the Castel Gandolfo lake from the Villa Palazzola's terrace. After the wood you will reach the little and joyful city of Nemi. Continuing the tour along the Francigena road you will arrive to the bank of the Nemi's lake, where you can visit the Nemus farm with its pic-nic area and its theatre of straw. Later you will reach Genzano, running along the old volcano you will arrive at Castel Gandolfo and its fantastic lake. Along the the lake's bank you can have a nice meal in the historic restaurant " i Quadri" and join its beach resort. After that passing through the lakefront you will come back to Grottaferrata travelling Via dei Laghi.
Fascinating tour for a complete trip of both lakes of Castelli Romani.