Skatanniemi is part of the Uutela recreational area. You can reach it by walking 40 minutes from Vuosaari metro station. If you come by car, you can park near the dog park. From there it only takes about 10 minutes by foot.
You will hike through pine forests and pass an old artillery station, till you reach the tip of the peninsula, which offers a wide view across the open sea and several islands. The narrowest point of the path is only one meter wide, between some private plots. The tip itself is owned by the city of Helsinki and allows everyone to move around freely and enjoy the romantic scenery.
The Skatanniemi patteri is a defensive structure, which was built in 1916 by the Russians to protect Helsinki from the east against attacks coming from the sea. If you are brave enough, you can bring a torch and explore the old shelters and ammunition stocks.