The Aa is a stream that runs through the entire municipality of Lille. This long walk mirrors that path. The goal of the hike is the Den Haert nature reserve, where the Aa will be your guide, likely along the most scenic part of its course.

On the way to Den Haert, you’ll follow quiet country roads, cross a suburb of Lille, and pass through the village center of Lille. The nature reserve was created from old peatlands that humans developed along the Aa. Nowadays, oak forests and alder carr forests dominate the landscape. Near the weir on the Aa stood the medieval motte-and-bailey castle Den Ouden Hofberg, a fortified residence of a local lord, built on a hill and surrounded by a moat.

On the way back, you’ll again walk a stretch along the Aa. The water of the river has a brownish color, which is normal. The soil in the area contains a lot of iron, which causes this coloration.

Eventually, you’ll reach the village center of Gierle, not far from De Lilse Bergen. After more than twenty kilometers of walking, you’ll have certainly earned a rest. You can enjoy this in the charming center of Gierle, where a summer bar is set up in the old gin distillery. Another resting spot is the historic tavern "In den Eik," where travelers have been stopping to relax for centuries.