Villa Aldobrandini

Villa Aldobrandini is a 2,500-square-metre nymphaeum built into the hillside above Frascati with fountains and terraces stacked on several levels, and an avenue that runs out of its gates, through the town, and lines the villa up with the cathedral. Grand Tour travellers called it the Regina Villarum; Goethe came and wrote about it. It is the only one of the grand papal villas still privately owned and lived in, and the water that runs its theatre arrives down an eight-kilometre aqueduct the cardinal built for the purpose.

Visit if you:

• want the Water Theatre -- the most ambitious hydraulic garden set-piece in the Castelli Romani, by Carlo Maderno and Orazio Olivieri
• are interested in how a garden organises a whole town: the axis through the gates continues as the Viale Catone
• like a building with its documents attached, from the inscription under the nymphaeum balustrade to the pre-Roman blocks turned up in the courtyard
• can accept a park rather than an interior: the house is a private residence

Skip it if you:

• want to see the Domenichino frescoes and the Apollo room -- they are inside, and inside is closed
• need fixed opening hours: access to the park goes through Frascati's tourist office, not a ticket window
• are expecting the whole garden intact. The top of it has been derelict since American bombing in the Second World War

This is somebody's house. Villa Aldobrandini is the only one of the grand papal villas that is not state-owned, and the family still lives in it -- which is why the interior is closed and why access to the park runs through Frascati's tourist office rather than a ticket desk. Arriving at the gate and expecting to be let in puts a private household in the position of saying no.

The fabric that is at risk is the waterworks. The Teatro delle Acque was damaged by American bombing in the Second World War, repaired in cement shortly afterwards -- a material that does not sit well with seventeenth-century stone and plaster -- and was in poor condition by 2011, when Prince Camillo Aldobrandini started the current restoration. The top of the garden has been derelict since the bombing and is not part of what a visitor walks.

The garden is also a working venue, hired for weddings, filming and events for up to 2,000 people in the grounds. The income is part of how a privately owned monument of this scale stays standing; the flipside is that a visitor may find the place staged, barriered or closed, and that is the villa earning its keep.

The villa is private property and the interior is closed to the public; the park can be visited by applying to Frascati's tourist information office. There is no ticket window and no published opening hours -- Villa Aldobrandini is the only one of the grand papal villas still privately owned, and the family lives in it, so a visit is asked for rather than bought.

What the owners do publish is the hire side, and it is worth knowing because it can close the place. The villa is let for weddings, filming, gala dinners, conferences and public events, with capacity for up to 300 people inside and up to 2,000 in the grounds, and tensile structures can be erected in the garden so that dinners go ahead under cover in any weather. A booking takes precedence over a visit.

Two parts of the site are not available on any terms. The interior -- the room of Apollo with its mosaics and Domenichino frescoes, the Cavalier d'Arpino frescoes, Taddeo Landini's Clement VIII -- is the family's home. And the top of the garden has been derelict since American bombing in the Second World War; restoration of the Teatro delle Acque fountains, repaired in cement after the war and in poor condition by then, began under Prince Camillo Aldobrandini in 2011.

Arrive on the axis if you can: the avenue that lines the villa up with Frascati's cathedral runs through the town as the Viale Catone, and walking up it is how the composition was meant to be met.

Everything at Villa Aldobrandini depends on the water being on, and the water is the garden's whole argument -- a 2,500-square-metre nymphaeum with fountains on several levels, fed by an eight-kilometre aqueduct. That makes the warm half of the year the point, and it makes confirming the visit in advance essential, because access to the park is arranged through Frascati's tourist office rather than by turning up. April to June and September to October are the comfortable months on a hillside above the Castelli Romani; the villa faces down the valley towards Rome, so late afternoon light is the view's hour.

The other variable is the villa's own diary. It is let privately for weddings, filming, gala dinners, conferences and public events, with capacity for 300 inside and up to 2,000 in the grounds, and tensile structures can be put up in the garden. A booking takes precedence over a visit, which is another reason to ask first.