Lake Ichkeul has been a Unesco World Heritage site since 1980, but it's been managed as a hunting reserve at least as far back as the 13th century. The lake's surrounds – marsh, floodplain and forested hills – are home to wild boars, jackals, mongooses, porcupines, foxes and otters, but the real attraction is the wide variety of bird species. In winter, migratory waterbirds descend on the lake in their tens of thousands.
Sign in at the entrance and then park at the old hot springs 3km further on. Boards give information not just about the wildlife, but the local tradition of women saying prayers to Oummek Dereb, a freshwater turtle that lives in the lake, to help them conceive.
Follow the path uphill to the Ecomusée, which has stunning views across the lake from both sides of the ridge it sits on. The Ecomusée has excellent displays on the lake and its wildlife. From here, you can walk right to look down around the headland to bring you back to the parking (a pleasant 30-minute stroll), or turn left to hike to a small series of caves (at least two hours round trip). There are also several birdwatching towers.
Park director Habib Gazouani can help you organise a guided tour, either with himself if he has time, or with one of the rangers.