This small national park off the coast of Alaminos, 35km southeast of Bolinao, actually consists of 123 separate islets (some are just large rocks). Over the centuries the tides have eaten away at the bases of some of these limestone islands, giving them a distinctive mushroom-like appearance.
Many visitors 'do' the islands in a day and only get to see a tiny fraction of what the park has to offer, but the Hundred Islands rewards patient exploration.
While visitors and fishing have taxed the local ecology, with coral damaged by dynamite fishing, the situation has been improving since the Alaminos city government took control of the park in 2005.