Synonyms for Imposing (same or very similar meaning)
WordNet sense 1 (impressive in appearance):
baronial, noble, statelyWordNet sense 2 (making a strong or vivid impression):
impressiveWordNet sense 3 (used of a person's appearance or behavior; befitting an eminent person):
distinguished, grand, magisterialWordNet sense 4 (having or expressing dignity; especially formality or stateliness in bearing or appearance):
dignifiedFrom the ODE community, based on WordNetadd/edit