Mentioned amongst the most important forts of the Marche region, the Fortress is the most representative monument of the town and is the most important tourist attraction. Presumably planned out during the rise of the power of the Acquaviva family, it was built around the 14th century. Giovanni Francesco Azzolino, after the destruction by Fermo's armed forces in 1447, was in charge of the reconstruction that was presumably supervised by the famous architect Baccio Pontelli. This Florentine architect had planned the fortresses of Offida, Jesi and Osimo. As a fine example of fortification, the Acquaviva fortress has an uneven square-shaped plan, that edges a large central court with a well and the angles armoured by towers. The highest tower, the Mastio, from which the sea can be seen at wide angle, is of cylindrical shape, 22 metres high, and has high angle slope underneath. The interior of the tower presents two rooms linked by a brick staircase; in these rooms an interesting permanent exhibition of old arms is currently located. The scenery that can be admired by visitors from the top of the Mastio tower in breathtaking; it opens up towards the wide sea horizon, the nearby hills, and the high mountain tops of Maiella and Gran Sasso. The tower where fire loopholes can be found, is diagonally positioned to the Mastio tower and is of pentagonal shape plan; it holds two rooms, placed one on top of the other, that open up onto the court. The other two towers, respectfully of pentagonal and square shape, were used for light weapons, as for example culverins and harquebus. In the higher parts, that can be walked upon through communication trenches, the defensive structure is set upon elegant corbels. A corridor with pill-box emplacements and a door at the end of the barrage, has been cut through the wall's width. The entire complex was restored at the end of the 19th century by the famous Marche's architect Giuseppe Sacconi, author of the Vittoriale in Rome. The style of the restoration seems to resemble Leonardo's principles and bear similarity to the ramparts of the 16th century.