31/08/2018 Observation Tower Negenoord, Dilsen-Stokkem De Gouden Liniaal Architecten Belgium The tower goes up in a former gravel extraction area now converted into the nature reserve of RivierPark Maasvallei. The outer walls were built with local materials – 20% gravel, 40% ocher-colored earth, and 40% clay, stabilized with trass – in seven