One of the current castles will be replaced

[DukeOfLorraine]

It was a generic unit, that was then modified to be Joan of Arc.

[Grandy02]

The other smaller Castle appears to be the Western European alpha version one.

In the AoK Heaven thread where the unused early castle designs were posted, someone asked Matt Pritchard whether there is a larger version of that image now posted by TommoChocolate. He answered:

I do not have a copy of that image, although I do know that we had wall posters made with that image on it. I have a few AoE and AoK posters in my possession, but not that one.

It appeared in this article, by the way.

@DukeOfLorraine

It was a generic unit, that was then modified to be Joan of Arc.

They actually look like the Joan model (from what I can see in the low-res image), which was derived from the early Cataphract. Though I’m not sure whether it was used for the Cataphract itself at some point.

[ZestySage992416]

This was a hint for Joan of Arc Civ which no one could catch.