Intramuros is one of the most important historic monuments in the Philippines, recounting the major part of the country's history itself.
This fortified city, built during the Spanish era then controlled successively by different invaders (American, Chinese, Japanese...), regroups different historic buildings which are very interesting. A little subjective list of places to discover: Fort Santiago, which is not to be missed, the insurmountable church of San Agustin, some passages on the ramparts, the beautiful reproduction of the Casa Manila and also the cathedral in Manila.
A museum and crafts centres can also be found there, as well as tricycle riders, nice and enthusiastic, which can be a good alternative to walking.
In any case, I recommend that you take your time, to roam the streets full of historic details and enjoy them. A must-see visit during your stay in the Philippines for those passionate about history and culture.