In the 12.-14. In the 13th century, the medieval Johannisburg was built here (based on 10th century stems), and added at the end of the 13th century to a chapel dedicated to John the Baptist.
Already at that time, the castle was the second seat of government of the powerful Mainz archbishops, leaders of the largest ecclesiastical province of the Holy Roman Empire and Arch Chancellor of the Empire. In the 13th to 15th centuries, Aschaffenburg was the venue of various princely assemblies and bishops' synods with outstanding visitors such as Emperor Ludwig the Bavarian or King Wenceslas of Luxembourg.
1552, the plant was looted during the Markgräflerkrieges and destroyed. Many existing art treasures were lost or destroyed. Many of Lucas Cranach the Elder's works have survived, today as part of the Staatsgalerie Aschaffenburg in the castle.
1604, the construction of the castle was commissioned by Elector Johann Schweikhard von Kronberg. The remains of the old castle were demolished - except for the keep. In the central axis of the castle a replica of the coat of arms of the elector can be seen - the original was destroyed during World War II.
The castle is strictly symmetrical and has external dimensions of 87.5 m x 86 m, the facade is made of red sandstone. The corner towers are 52 meters high, which corresponds to the width of each wing. Noteworthy are the three-storey gables in the central axes of the intermediate buildings with an elaborate ornamentation in the style of Italian Renaissance architecture. The castle is surrounded by a dry moat, accessed via a bridge in the southeast.
From 1614 Johannes Schweikhard von Kronberg carried out the affairs of state of the new castle. For the inauguration he had minted coins that show the castle and its coat of arms. 1618/1619 then the last work was completed. The apartment of the Elector was on the first floor in the main wing and in the southeast wing was housed the silver chamber. Here are u.a. Original furniture of the Archbishop Friedrich Karl Joseph von Erthal from the period around 1800 shown. As a residence for the emperor, the "Kaiserappartement" including the very prestigious Kaisersaal was on the second floor.