Walk the walled city to see Spanish colonial architecture and the historic fort; Fort Santiago typically open 8:00–18:00 so plan mornings for cooler weather.
Half-day island hopping tours typically depart morning to mid-afternoon — some operators run later trips; check local operators for times and availability.
Iconic Hindu caves and giant Murugan statue just north of the city; site typically open early morning to evening (best to visit early to avoid heat and crowds).
If you want rides, SkyWorlds is the pay-entry theme park (opens mid-day often); SkyAvenue shopping offers dining and entertainment if you prefer a relaxed visit.