Took this shot at a client's office today, where you can glance from high above to the restricted Lake Ülemiste. Why restricted? It's one of the main water reservoirs for the people of Tallinn.
In the small patch of forest right before the lake, there are health and nature trails that extend towards the other side of the lake if you want to go for an evening run or bike ride. I've even seen edible mushrooms there.
Towards the other side of the lake a bit, there's the water purification plant, laboratories and offices. I'm lucky to have managed myself on a tour there a few years back when they had open house, and I very much recommend this to everyone if the opportunity comes up again.