The almost square castle site is surrounded by moats. Until around 1550 the fortress at the northwest corner of the town was incorporated into the town fortifications. North of the castle, is the only surviving medieval town gate, the Saltor Tower (Saltorturm). In the 16th century a modern bastioned fortification, based on Italian designs, was constructed in front of the remains of the medieval town wall. North and west of the castle district, two large casemated "Old Italian" bastions escaped the fate of demolition that other parts of Forchheim Fortress suffered in the 19th and early 20th centuries.
Large parts of the main house and the courtyard buildings go back to the 14th century.
The eastern part of the main house is joined to the courtyard buildings on the west side by walls and timber-framed passageways. The two upper storeys of the northwest wing have also been executed in a simple, timber-framed style as far as the castle courtyard.
In the middle of the 16th century the urban castle was remodelled. It was at that time that the picturesque, timber-framed walkways on the curtain walls were constructed. In 1603 work began on building an octagonal staircase tower in front of the four-storey main house. The mighty half-hipped roof of the main house dates to the 18th century. Originally the east wing was covered by a gable roof with crow-stepped gables. Since 1768–69 a sandstone bridge has spanned the moat in front of the gateway on the south side. Previously access had been protected by a drawbridge. Next to it, a rectangular Renaissance oriel with a shed roof enhances the architectural impression. The rather austere south front of the ensemble is brought to life mainly by the timber framing (Sichtfachwerk) above the gateway. A typical Franconian motif is the frieze made of numerous, small curved St. Andrew's crosses underneath the window area.
On the east façade of the main wing are three reliefs depicting coats of arms. On the second storey is the official coat of arms of Prince-Bishop John Philip of Gebsattel. The third storey bears the coat of arms of Bishop Lamprecht of Brunn and the Hochstift. A high medieval sculpture of a basilisk has been engraved into the south wall; it has been dated to the 12th century.
The addition of a modern, steel and glass staircase and lift tower in the north of the east wing has been highly controversial. This feature was needed to turn the castle into a museum.
The East Wing of the castle is divided into two parts by a transverse wall running the width of the building. The north part is somewhat larger than the south part. The barrel-roofed cellar goes back to the 14th century. The ceilings of the two halls on the ground floor are borne on sandstone columns.
The flat ceiling of the north room rests on a round column and a wooden beam. The south part was vaulted later, resulting in a twin-aisled hall comprising four bays that are covered by cross vaults. In former times a passageway led from here to St. Mary's Chapel. On the walls of the hall fragments of fresco-secco (painting on dry plaster) from the period around 1400 have survived, which are stylistically related to contemporary Bohemian art. A fragment shows the Biblical and historical figure of King David of ancient Israel. Like the murals in the other halls these paintings are among the most important Gothic murals in South Germany.
The chapel was originally located in the southern part of the first floor. The vaulting was done in the early modern period; and the hall was divided by an internal dividing wall. The murals of the old chapel have survived and indicate its original function and arrangement. It includes depictions of the prophets, the Adoration of the Magi, the Annunciation and the Last Judgement. Two paintings with secular content have been interpreted by H. Kehrer as referring to the weak king, Wenceslaus. The paintings were clearly done by different masters. The Adoration of the Magi, again, appears to be derived from the field of Bohemian art. The Last Judgement, by contrast, is in the latest Forchheim style, which was derived from the Nuremberg art of the early 15th century. The northern hall, like that on the ground floor, is covered by a flat ceiling which, however, rests on wooden beams.
On the second floor of the northern end of the wing is also a twin-aisled, flat-ceiling hall with a wooden centre beam. The architectural paintings were done by Jakob Ziegler in the years 1559–60. The south room is likewise a two-aisled hall. The flat ceiling is supported on an octagonal centre frame. The murals, of various themes, were also created by Jakob Ziegler. One of the paintings shows Saints Henry II and Cunigunde with the model of Bamberg Cathedral (drawn in 1599, south wall).
The third floor was conceived as a storage area and currently serves as a museum depot. The old staircase tower hides a stone circular staircase which opens into the northern part of the east wing.
The West Wing, the former side wing, acts as offices for the castle museums. No significant historical interior features have survived here.
