Jayapura City Hill is one of the best easy viewpoints over Jayapura, looking down across the city and the bay that wraps around it. The comparison locals make is to classic city-overlook parks elsewhere: the appeal is simple, wide, and immediate.
Go when the weather is clear, preferably early or late in the day when the light is softer and the heat is less punishing. It is a straightforward stop to combine with other sights around town.