Complex sentence: Cerin Amroth, also known as the mound of Amroth, is where elanor grows, that stood in the heart of Lothlórien where stood the house of Amroth before he was lost.
Split into simpler sentences: Cerin Amroth, also known as the mound of Amroth, is where elanor grows. It stood in the heart of Lothlórien where stood the house of Amroth before he was lost.