Orford Castle - England
Orford Castle is a 12th century castle located in Suffolk, England (East Anglia, a "bit" North of London). The castle itself did not survive, but the central keep is an impressive, thick walled tower with 5 floors and a useful roof. (Much more at https://en.wikipedia.org/wiki/Orford_Castle and in https://www.english-heritage.org.uk/visit/places/orford-castle/ )
The presented plan is of the keep as it stands today. Some elements have changed through the ages - arrow slits became windows and in modern times the roof was changed to a flat concrete slab, one of the smaller towers hosted a Radar antenna in WWII.
Very little "special" tools were used in the drawing , most of it is lines drawn over a scanned plan.
Basement - actually above ground, but has no external access. Has a well and maybe a prison cell.
First (and Second) floors - Lower hall (two storeys), external stairs lead to the gateway and entry hall. The Lower hall is 2 stories high, while several chambers and spiral stairs are built into the thick walls.
Second floor - A chapel.
Third floor (and Fourth) - Upper hall (two storeys). The main hall of the Keep, it used to have some sort of a wooden gallery or stairs (not in the current plan). There is an exit to the roof of the chapel.
Forth floor - a water cistern (yay in-door plumbing ;-) and a room that has access only from the missing wooden gallery.
Roof - used to be a conical wooden construction, now it is a flat concrete slab. Has 3 small towers, one of which is the keeps ovens. The older crenelations are lost.
Tower tops - Walkways and crenelations.