From the first half of the 18th century, the outer edge of the castle glacis was used as a promenade by the inhabitants of Gisors. It was at their request that Fouquet de Belle-Isle, Duke of Gisors, agreed to plant some of the first trees to adorn them.
It was not until the mid-19th century that Monsieur Thierry, mayor of Gisors from 1848 to 1862, transformed the fortress and its walls into public gardens.
Today, the gardens and avenues of Château de Gisors are a pleasant place to stroll along the shady, centuries-old avenues lined with beech, elm, lime, chestnut and plane trees.