St. Ignatius Hill is formed by limestone rocks of marine origin, rich in fossils, mainly bivalve mollusks dating back to the Miocene. On one of these rocks rests the Lazzaretto Tower, also called the Parsley Tower (34 m above sea level), built before 1600. The tower controlled the entrance to the ancient ports of Cagliari and guarded the Lazzaretto. From the Prezzemolo Tower the path leads to the World War II anti-aircraft battery formed by six emplacements that housed the cannons and machine guns. A mosaic made in the Venetian style is still visible in the command room. The tunnels that were used as ammunition storage and shelter during bombing raids can also be visited. Leaving the antiaircraft battery, the excursion continues to the Fort of St. Ignatius (18th century 94 m above sea level), built in anticipation of the war against the French (1792-1793); after its disarmament it was used first as a branch of the Lazzaretto and later during World War II as a listening post for aircraft passage. Along the path, between the Lazzaretto Tower and the Fort of St. Ignatius, it is possible to admire typical plants of the Mediterranean flora such as mastic tree (used in the past for extracting oil from its berries), juniper, cistus, euphorbia (used in the past for poaching), as well as medicinal herbs such as thyme, helichrysum, sea wormwood, etc. The hill takes on different colors according to the seasons, thanks to the presence of some weed-like plants such as iris, blue borracine, broom and others. During the hike, it is possible to admire the different views of the hill, such as Poetto, the salt pans, Calamosca and the city.
