“Ravana was very advanced materially, so much so that he turned his kingdom, Lanka, into pure gold, or full material wealth. But because he did not recognize the supremacy of Lord Ramachandra and defied Him by stealing His wife, Sita, Ravana was killed, and all his opulence and power were destroyed.” (Shrila Prabhupada, Shrimad Bhagavatam, 2.7.23 Purport)