It's a walk through closet. It leads into the ensuite on the left (behind the bedhead) and into the rest of the apartment on the right of this doorway. I'd say the space would be around 2m/2.5m long and 1.7m wide. The partition wall is masonry but is only 1 brick wide or somewhere between 120--140mm thick.
Hope that helps your design development. Thanks for the complimentary feedback too. :)

it helps! thanx for an explanation! the concept is great!