The town is located within the Regional Natural Park of Opal Caps and Marshes, between Calais (17 km away), Boulogne-sur-Mer (23 km away), and Saint-Omer (38 km away). It is close to the secondary hubs of Guînes to the northeast (5.5 km between the centers of the two towns), Marquise to the west (10 km), and Licques to the east (12 km)

The essential

— Le tilleul du Crocq

After the February 1848 Revolution, tree plantings of Liberty Trees took place. This was the case in Fiennes, where the Crocq lime tree was planted. It marks the entrance to the village with a roundabout. It was classified as a natural monument in December 1930. Therefore, any pruning or construction near the Crocq Lime Tree requires prior approval. Located at the intersection of two streets in the village, its base is surrounded by a circular wall made of Boulogne stone (a site classified by decree of January 20, 1923).