It has a combination of long and difficult terrains, a wealthy rain forest, a vast diversity of plants and animals, spooky stories, and unpredictable weather conditions, which can bring a remarkable hiking experience (the reason why it's my hardest). So far, hiking Mt. Halcon in Oriental Mindoro is the toughest. Though this mountain garnered a nine over nine rating in terms of difficulty, it is part of my "list of the must hiked mountains" because of its hidden and majestic beauty.
