My list is growing too!
You are correct about North Luzon. Although I've seen quite a few areas, there are still so many more! The trip along the north coast from Aparri to Laoag via Pagudpud was amazing, but I need to complete the loop down to Subic via Vigan and La Union. There's also Bataan and the whole mountain region (apart from Baguio) that I still need to see.
But for a real adventure, the East coast of Isabela would be amazing, but it's one of the most remote and difficult areas to reach in the Philippines.![]()