A gentle mist wafts over the cobalt waters of Lake Nemi, rising to kiss slim reeds, the bright flowers of yellow iris, and thick copses of plane trees. Up it travels, above the ancient craters filled by the lake towards intricate woods of holm oaks and chestnut trees, over flower-strewn valleys and above the soaring belfry and genteel houses of Genzano di Roma.

Lake Nemi’s cobalt caldera and the tree-lined streets of Genzano above it are one of the prettiest sights in the Castelli Romani, a clutch of villages and towns south-east of Rome which has been a rural retreat for affluent Romans since the days of Julius Caesar.

Originally a Roman settlement and later a medieval village, Genzano was given a new look in the late 17th and early 18th centuries by duke Giuliano III and his daughter Livia Cesarini. The two built a new model town around the borgo’s old medieval heart, opening up vistas, bringing in trees and giving a new façade to old buildings. To this day, part of Genzano’s charm lies in the Baroque geometry of the elm-lined streets conceived by the duke and his daughter, the sober lines of the Capuchine friars’ church they renewed and the grandiose ducal palazzo where they lived, which Livia’s son, Gaetano, further expanded and embellished.

The stretch of quiet countryside below Genzano is perhaps the best place to explore the area and take in these views. It is here that Knight Frank are selling a lovely old casale with five bedrooms, which is not only close to Genzano and Lake Nemi, but also within easy reach of Lake Albano, the summer papal residence of Castel Gandolfo and the wine-making town of Frascati.

“Situated in a wonderful location, the property provides excellent access to both Rome city centre and its airports, as well as the coast and neighbouring towns,” says Rupert Fawcett of Knight Frank.

A deep red façade clad with bougainvillea overlooks a paved courtyard with plenty of space for alfresco dining. Inside, the interiors are full of rustic charm, with beamed ceilings, wooden doors and shutters, and tiles in a warm cotto hue.

The windows frame verdant country views over vineyards and olive groves - some of which are the property’s own. The casale comes with about 21 olive trees and a large vineyard, a front garden with tall cypresses and palm trees and a south-facing patio with swimming pool.

All this makes it a good buy “either as a private holiday home or as a rental option,” says Fawcett.

The asking price is €750,000. For more information, contact Knight Frank on +44 (0)20 7629 8171 or visit www.knightfrank.com.