i think it takes more than 3 hours.I spent 2 and half hours on Kent Ridge park and horti Park. Including jungle trekking in kent ridge and Reflection of Bukit Chendu musuem. Camera battery got dead half way, so I didn't take many photos in Horti park. From the map, i assume Teloh Blangah Hill Park and Mount Faber should take more time than Kent Ridge does.