IRONMAN Triathlon 70.3 Subic Bay 2021. Bounded on three sides by a mountain range and endowed with a deep natural harbor, Subic Bay was once the home base of the U.S. naval forces in the Pacific. The area is now a premier holiday destination for visitors from all over the world who come for its pristine beaches, first-rate amenities, and friendly services. Subic Bay is one of the best places to train in the Philippines.