They are chimneys.
I was thinking of colouring and shading the roofs and then adding some extra drop shadows on higher buildings to better show the multi-levels. I wanted to redo the landscape and streets now that I am better with textures. Put some boats in the harbour and so on. The chimneys will blend better once it it coloured and shaded. I can always make a greyscale version from there. (Just for you Katto)
I am hoping to turn this into something really special.