 Tower 1 , nicknamed " Hat Tower " ( Šešir @-@ kula ) , is one of the oldest towers , and doubles as citadel and dungeon tower . It has an eight @-@ sided base with a circular spire rising from it and a square interior . The next tower to the west , tower 2 , is completely circular in shape . The third tower has a square base , with the open side facing the dungeon tower to the north . On the top floor is a terrace that overlooks the Danube and the entrance to the Iron Gate gorge . Down the slope from tower 3 is tower 4 , which also has a square base . The ground floor has a Serbian Orthodox chapel that was built into the tower , rather than being added later . The last tower along this wall , tower 5 , is the only tower to remain completely square . 
