Paris' mythic La Sante prison opened its heavily guarded doors to visitors Sunday as part of the country's annual Heritage Days festival.

Opened in 1867, the huge brown edifice in Paris' 14th arrondisement has held some of France's most notorious criminals, including the international terrorist known as "Carlos the Jackal," Nazi collaborator Maurice Papon and rogue trader Jerome Kerviel.

Visitors were allowed behind the prison's tall, razor-wire-topped walls and led in small groups to see first-hand what the interior of Paris' only remaining prison looks like.

The prison is largely closed for renovations expected to last five years. Once holding more than 1,000 prisoners, La Sante now houses 100 prisoners on a work-release program.

Heritage Days is an annual event that allows free access to numerous monuments and official buildings.