basic Barbican

A barbican is a type of fortified gateway used in castles to protect the weakest part of a castle in the event of a siege: the entrance

They consisted of 2 tower-like structures that where extended towards the center of the castle and held supplies of weapons & arrows, stones and wood to throw to the attackers through holes in the floor of the 2F called "murder holes", and often held food supplies in case of a prolonged siege, to allow certain independence in an emergengy during a siege.

They often had 1 or more porticulli among the 1 or more pair of heavy and sturdy doors, used both as a defensive barrier and as a trap, closing the innermost first letting the enemy advance towards it, and then closing the outer one in their back, effectively trapping them so the guards could throw arrows, stones, and burning wood to eliminate them

It normally had a stable garrison watching the surroundings, and also ussually housed a few officers or guests and could have meeting halls or reading rooms in some of its floors

In this version i put the main weapons&arrows supplies plus some food supplies in the 1F.
In the 2F i put the rest of the armory and a couple of rooms for officers (with regular beds but silk-like sheets and modic study and wardrobe).
In the 3F i put two more important rooms, mainly for nobility guests (with elaborated beds, silk sheets and bigger desk and wardrobe) and a library with 3 bookshelves and a central reading table illuminated by 3 large windows and a couple smaller ones in front of it

In the top there may be built counter-siege equipment like mangonels or ballistae to attack either enemy soldiers or enemy siege weapons from it... if there was enough space