I once took an overnight train to Kuala Perlis to catch the early ferry to Langkawi. I wanted to tick off the last Malaysian state I hasn't until then visited. Tiny and tucked right up under a crease on the Thai border, I had Perlis covered, I ignorantly thought, with a mad dash through the street-food vendors thronging the port. 

Fast forward 10 years and the whispers about the extraordinary landscape of the Wang Kelian Valley in Perlis were insistent. Hypnotic, abundant, untouched. What had I overlooked all these years?