He was strongly influenced by meeting and working with Gabrio Serbelloni, who was sent to Cortona by Cosimo I de' Medici, Grand Duke of Tuscany to provide for the city's defenses during the conflict between Florence and Siena.

[citation needed] In 1560 Francis Laparelli was called to Rome by Pope Pius IV, at the request of his cousin Serbelloni, with the task of restoring the fortifications of Civitavecchia.

The Grand Master Jean Parisot de la Valette determined to rebuild, choosing the high ground of Mount Sciberras as the site for the new fortress.

He said that the fortications at Birgu, Senglea and St. Elmo had suffered so badly that four thousand laborers working 24 hours a day would be needed to make basic repairs.

[4] Laparelli laid out the town plan based on a grid pattern to allow sea breezes to flow through the city more easily in the summer, and designed the drainage system.

[5] The final proposal, published on 18 June 1566, was for a fortified city that extended up the peninsula to Fort Saint Elmo, with four bastions and two cavaliers guarding the landward side.