Stavelot, Trois-Ponts, Vielsalm and numerous other historical sites in the surrounding area are well worth a visit. Baraque de Fraiture and Val de Wanne should also be included on your list.
Spa is well worth a visit in its own right. But the "Thermen van Spa" spa facilities are also a refreshing getaway for enthusiasts, and last but not least, there are numerous events at the Circuit de Spa-Francorchamps, with the Formula 1 race being an absolute crowd puller.