The Plaza de Prim square, the site of the lovely Fortuny theatre, before going on down Calle de Monterols to the Plaza del Mercadal square. This is the site of the Casa Navàs building, a Modernist jewel designed by Doménech i Montaner which still contains period furniture, coffering and lamps.
http://www.spain.info/en_IN/que-quieres/ciudades-pueblos/otros-destinos/reus.html