View along the "Viale dei Ninfei" within the gardens of the Papl summer residence of Castel Gandolfo. Left of the alley the retaining walls of the uppermost level of the ancient villa of Emperor Domitian can be seen. The alley itself is located at the medium level, the "Giardini del Belvedere" (which cannot be seen on this picture) lie on the lowest level of Domitian's villa.