Mount Jasen Observatory offers a great view of Kozjak Lake with no hiking required, but you can hike around if you want to! It’s about an hour car ride from Skopje, and well worth the drive.
Google Maps and Waze both have the location as “Kozjak Lake Observation Point. There is cell phone service most of the way, including at the top. We only lost service for a few minutes right before the top.
There are several pull outs on the road, and I recommend stopping at a few to get different views. I also highly recommend hiking around a bit if you’re up for it.
A few of my favorite photos are below: