Complex sentence: The "Huaca del Sol", a pyramidal adobe structure on the Rio Moche, had been the largest pre-Columbian structure in Peru; however, it was partly destroyed when Spanish Conquistadores mined its graves for gold.
Split into simpler sentences: The "Huaca del Sol", a pyramidal adobe structure on the Rio Moche, had been the largest pre-Columbian structure in Peru. However, it was partly destroyed when Spanish Conquistadores mined its graves for gold.