added the final tower, complete with cannon embrasures and galleries. Upper compound The upper compound (A) is the oldest part of the fortress. It includes the citadel (tower 1) and the Serbian Orthodox chapel (tower 4). Although it remains uncertain, the chapel has led many to believe that this section was built by a Serbian noble. Later, during either Serbian or Hungarian rule, the fortress was expanded to include the rear and forward compounds. Rear compound The rear compound (D) is separated from the upper compound by both a wall connecting towers 2 and 4, and a steep rock high. Next to tower 5 is a building (VII) which was probably used as a military barracks and for ammunition storage. Forward compound The forward compound was split into lower (C) and upper (B) parts by a wall linking towers 4 and 7. The entrance (II) is in the lower part, guarded by towers 8 and 9. Tower 8 has, in turn, been fortified with a cannon port. Opposing the entrance was a second portcullis that led to the rear compound. Along the path was a ditch wide and deep which then became a steep decline. At the outer end of the lower part, and connected to the 9th tower with a low wall, is tower 10, which the Turks added to act as a lower artillery tower. It controlled passage along the Danube and guarded the entrance to the harbour, which was probably situated between towers 5 and 10. There are remains connected to tower 8 which probably formed a larger whole with it, but the lower part did not otherwise contain buildings. In the wall that separated the upper and lower parts was a gate that led to the upper part. The upper part did not have buildings, but there remains a pathway to the stairs up to gate IV, which is off the ground, right next to tower 3. Towers The first nine towers are high. In all ten towers, the floors and stairs inside were made of wood, while external stairs were made of stone. Half of the towers (1, 2, 4, 5, 10) have all four sides and are completely made of stone, while the other half (3, 6, 7, 8, 9) lack the side facing the interior of the fort. Tower 1, nicknamed "Hat Tower" (Šešir-kula) by Austro-Hungarian traveler Felix Kanitz in the 19th century,