Manila, like many other large Asian cities is taxing on the nervous system. It can be brutally hot and humid, it is extremely polluted, and the traffic is some of the worst I have ever experienced (I would compare it to that of Bangalore, India). The humungous shopping malls can offer some escape from the traffic and the madness, but even the malls are usually crowded!
But there is a place for reprieve and you can find it in Intramuros. Intramuros is the oldest district and historic core of Manila, so there is a lot of history here. The walled city is the only district of Manila where old Spanish-era influences are still plentiful.
There is Fort Santiago and Rizal Shrine which are definitely sites worth touring. José Rizal, the Philippines' national hero, was imprisoned here before his execution in 1896.
There are wide open spaces and when you are on the grounds of Fort Santiago the hustle and bustle of Manila seams to disappear.