I have no idea what to call those things otherwise.. I mean you put the battlements on top of the walls, and there are small pillars to put in between those battlements to fill the gaps. I think there would be more than eight of them in the 3666.
They are called Battlement Columns, cost 0.45 euro each and are part number 30076770. (On old sets where the last group of figures in a part number consists of three figures, you need to add a zero to the end.)
If you go to playmobil.com and go to the UK site and scroll down the page, two lines above the link to Building Instructions, there is one Find Spare Parts. Click on this, enter the part number and it will tell you if it's available and, if it is, how much it costs - but remember, if the part number you have is only seven figures, add a zero to the end, oh, and put the figures in as one string, not 30 07 6770, but 30076770.