Any of the lakes in Copenhagen is worth your time. I love when you can be by the water in the middle of cities and the Lakes and here Peblinge Sø is one of them. I used to run around these lakes while I was living in Copenhagen and I loved it. The paths around the lakes are good and easy to run on, flat and not to hilly so it is great for beginners to run on. It is even a very romantic place to take a stroll around when the sun is setting and the sky is turning red. They are not great to bathe in though as not only is the water dirty and filled with bikes and what ever else is in the city and the lakes are to shallow to be swum in. But even if you can not bathe in the lake it is still worth having in the city as it gives a sense of space and nature even in the middle of the biggest city of Denmark.