Drawing the details of a building.
This is a video in which you can see me working on the details of my pencil drawing of Christ Chruch Cathedral in Montreal. You can see that it is very important to create shading and lighting in the correct places. Bricks used for very old buildings have an extremely rough surface, and you can create this texture by making a lot of contrast. The smoother stone, doesn't contain a lot of contrast, so all you have to do is just make the whole surface equally dark or light, depending on how much light is hitting that part.
Creating contrast in between lighting and shadows, is a very important pat of making realistic pencil drawings.