Yes, there is a lake on the north side of Phoenix!
If you are looking for something unique and interesting to do in the PHX area, I recommend taking a tour on Lake Pleasant Cruises. The cruise boat is top notch, the staff is very friendly, and the bar is well stocked. The captain does good job narrating the trip and explaining the history of the lake. The tour time is just right. I settled on 5 stars because the lake is more beautiful than I expected.