Kastel is the historical bridgehead of Mainz, the capital of the German state Rhineland-Palatinate and is located on the right side of the Rhine river.

The separation from Mainz is the issue of intense debates by local patriots in three districts (Kastel, Amöneburg and Kostheim).

Many Kastel residents feel like they belong to Mainz which reflects, apart from the administrative affiliation, the reality of everyday life.

The three mentioned districts of Wiesbaden still bear the designation "Mainz- ..." because until today no closed formal legal act has been made up.

At that time, the Romans built a wooden bridge across the Rhine connecting Moguntiacum (Mainz) with a castle on the right bank of the river.