Modave is a municipality of Belgium. It lies in the country's Walloon Region and Province of Liege. On January 1, 2006, Modave had a total population of 3,722. The total area is 40.37 km² which gives a population density of 92 inhabitants per km². The magnificent "Château des Comtes de Marchin" or Modave Castle is situated near the village of Modave. Rennequin Sualem built here the model of the famous Machine de Marly which he invented.