Walk up the stairs of the 'Esslinger Burg' which was built in the 13th century. While climbing up you'll have a stunning view of the city which will make it worth it. At the top you can find a restaurant in the tower, a playground and in summertime open air cinema events.
The top of the 'Burg' offers the best view of the city. You can see all the way from Altbach, a neighbouring village, to the west part of the city called Mettingen. You can definetly take stunning pictures here.
Be prepared for over 300 stairs. But it's worth it!