The fortress as it presents itself today follows the shape of an oval earth mound: an ancient hillfort which had already been established here in prehistoric times as a defense system. The southern exterior wall with two projecting turrets and a decked wall walkway extends from the west gate tower located at the gateway to the semi-circular tower to the east. The kennel behind is a typical element of medieval fortifications: if attackers were able to overcome the outer moat wall, they were encircled in the kennel and an easy target for the defenders of the battlements on the main wall. In peacetime, the kennel served as a shelter for foreigners and neighboring residents in need of protection.
The entire castle is dominated by the imposing castle keep which is already visible from a far distance. The south-facing loggia, originally from Venice, shows a stylish arched middle column of the 14th century and offers a magnificent view towards Vienna. Adjacent lies the so-called Gaden, which served as a storage building as well as a bedroom. In the West, the castle was protected from attackers through the deep moat and the drawbridge which folded up against the castle gate, locking the access to the kennel behind. For defense purposes, the western part of the castle and the rectangular castle keep were built at an acute angle to the gate so that enemy projectiles could not hit the wall head-on, but bounced off the inclined surfaces. The western castle section is harmoniously completed by the gothic bell tower and the chapel with its impressive arched window behind the organ loft.
In addition to its protective function, the moat of Kreuzenstein holds a special secret: the entrance to an underground passage which was carved at the time of the reconstruction to gain building material from the bedrock. In a cave at the beginning of the resulting tunnel, an extraordinary exhibit is suspended from the ceiling that recalls both the hunting passion of the founder of Kreuzenstein and his polar expedition in 1872: the gigantic skeletal remains of a bowhead whale. The tunnel has been enlarged and serves as a 200m long escape route towards the Danube.
From a position in the castle’s outer courtyard, the servants' hall is located in the western part of the building, which served for boarding and accommodation of staff and guests of lower ranks. East of the gate tower are the horse groom chamber and the stables. The architecturally impressive inner courtyard of the castle, which is surrounded by the building of the great hall, the northwest tower, the chapel, the dungeon and the so-called Gaden, is accessed through the outer courtyard by a pointed arch.
Above the pointed arch connecting the two courtyards, the so-called Kaschauer Passage is located whose magnificent gothic arches and tracery breastwork originate from the organ loft of the Cathedral of Saint Elizabeth (Košice Cathedral) in Košice in Eastern Slovakia. Other characteristic elements of the inner castle courtyard are the magnificent lime tree which was personally planted by Count Johann Nepomuk Wilczek during the restoration of the castle and the covered well reaching down to a depth of 60m whose casing and wheel originate from Venice. During excavation work in the old well shaft, an ancient Jewish grave stone from the 13th century was salvaged. The courtyard wall is characterized by decorative elements such as medieval stone sculptures, sepulchral monuments and ornamental stonework. The historic iron rings mounted on the wall are a vivid reminder of the castle’s former function as a fortress and a focal point of chivalrous life: they were used to tie the horses.