sentences:  Its stylistic hallmark is the ornate pillared "Kalyanamantapa" (marriage hall), "Vasanthamantapa" (open pillared halls) and the "Rayagopura" (tower).Artisans used the locally available hard granite because of its durability since the kingdom was under constant threat of invasion.While the empire's monuments are spread over the whole of Southern India, nothing surpasses the vast open-air theatre of monuments at its capital at Vijayanagara, a UNESCO World Heritage Site.