His solar is just this side of it

The "just" belongs in there. It means "next to it, on the side of it that is nearest to us". Without "just" it would mean "between us and it, probably nearer to it than it is to us".

Imagine - Change the sentence into a picture. In the picture, there is a road. You are standing in the road. One kilometer away is the King's tower. On "just" "this" side of "it" is the solar.
The word "Just" has many meanings. In this case, it means Near, Close To or Straight Across From. It is impossible to tell exactly where, but it is known to be close and not far away.
"This" is lik

CliveHi,What does 'his solar' mean?Clive

http://www.castlesontheweb.com/glossary.html

It is the Lord's living area, often above the Great Hall. (I didn't know, either.)

stephenlearnerThe tower farthest from us, on the southeast corner, is the King’s tower. His solar is just this side of it.

X = 'his solar'

On the other side of the tower (from us):

us -------------------------------------------------------- tower --------------X

Just on the other side of the tower (from us):

us ------

Thank you all, especially Jim, for your help.