Mongiardino, second from right, examines plans at the Lake Lugano project.

A rendering of the villa’s entrance hall.

The completed entrance hall.

Lee Radziwill at Turville Grange, her Mongiardino-decorated english country house, in 1971.

The initial sketch for the library ceiling.

An artisan highlights the villa’s library ceiling.

The end result, with the plaster treated to resemble painted wood.

Laura Sartori Rimini and Roberto Peregalli in their Milan studio, with the model of the Swiss Villa and related archival materials.

In 1962 Mongiardino combined two spaces at his Milan apartment into a Gothic Revival–themed sitting room and library.

Islamic-style tiles and textiles—all of them executed in trompe l’oeil—wrap an orientalist bedroom that Mongiardino designed in the early 1980s.