The Château d'If and neighboring offshore islands seen from Marseille

The Chateau d'If from a boat

View from a cell in the Château d'If

The Château d'If is located on the small island of If, situated about a mile offshore in the Bay of Marseille, France. It is a square, three-storey building 28 m long on each side, flanked by three towers with large gun embrasures. The remainder of the island, which only measures three hectares, is heavily fortified; high ramparts with gun platforms surmount the island's cliffs.

It was built in 1524-1531 on the orders of King François I as a defense against attacks from the sea. However, its construction was extremely controversial. When Marseille had been annexed to France in 1481, it had kept the right to provide for its own defense and the castle was therefore seen by many of the local inhabitants as an unwanted imposition of central authority. It was put to the test in July 1531 when the Holy Roman Emperor Charles V attempted to attack Marseille. His invasion was abandoned, due partially to the castle's strength.

The castle never had to fight off an attack, which was perhaps fortunate. The military engineer Vauban wrote a scathing description of the castle in 1701: "The fortifications look like the rock, they are fully rendered, but very roughly and carelessly, with many imperfections. The whole having been very badly built and with little care... All the buildings, very crudely done, are ill made."

The Château d'If's isolation made it ideal as a feared prison for political and religious detainees. Over 3,500 Huguenots (French Protestants) were sent to If, as was Gaston Crémieux , a leader of the Paris Commune, who was shot there in 1871.

The island became internationally famous in the 19th century when Alexander Dumas used it as a setting in his novel The Count of Monte Cristo, published to acclaim in 1844. In the book, the Count (actually the commoner Edmond Dantès) and his mentor, the Abbé Faria, were both imprisoned on If. After fourteen years, Dantès makes a daring escape from the castle, becoming the first person ever to do so and survive (in reality, none did). He sets himself up as the Count of Monte Cristo and takes revenge on those who had falsely sent him to the island, driving them into bankruptcy and suicide.

As was common practice in those days, prisoners were treated differently according to their class and wealth. The poorest were literally at the bottom of the pile, being confined to a windowless dungeon under the castle. The wealthiest were much better off, living comparatively comfortably in their own private cells (or pistoles) higher up, with windows, a garderobe and a fireplace. However, they were expected to pay for this privilege, effectively forcing them to fund their own incarceration.

The castle ceased use as a prison at the end of the 19th century. It was demilitarised and opened to the public in 1890. It can now be reached by boats from Marseille's old port. Its fame as the setting for Dumas' novel has made it a popular tourist destination.

Perhaps because the real Château d'If has only a modest visual impact, other locations have stood in for it in film versions of Dumas' story. In the most recent adaptation starring Jim Caviezel (and released in 2002), the castle was represented by St Mary's Tower - a watchtower on the cliff edge of Comino, the smallest of Malta's islands. It can readily be seen on the ferry crossing from Malta to Gozo.