Why didd the ancient greeks believe that natural places like springs and tree groves were important

They believed that spirits were guarding the tree groves and springs as their inhabitant hence they remained sacred.

The ancient Greeks accepted there were a large number of divine beings and goddesses. Lord of divine beings and goddesses was Zeus. He could control the climate and was frequently called 'the thunderer' or 'the cloud-gatherer'. He lived with the other gods on Mount Olympus, a high mountain in northern Greece.