An extensive canal system runs from just west of the center of Brussels north and south. The sections near the center are OK for running, but quite busy and there is not a seamless pedestrian trail. The most pleasant sections close to the center are from the Porte de Ninove, at the intersection of the N8/R20. Head south from here for miles. It gets especially nice and runner-friendly south of Anderlecht. There are bridges to cross from one side to the other, and paths on both sides, in areas. Another bonus is that there are buses and trains that run along the N6 paralleling the canal, so run one-way to Halle and hop on a train back!