I’m going to show you two real existing castles and for each of them a different way to draw them. The first is in Manzaranes el Real, in the middle of Spain. This castle from 1475 consists of two enormous floors with three mighty towers on top.
Exercise 1: build the Spanish castle following the next steps. Don’t draw the ground line too close to the bottom edge of your paper. Draw each step before moving on to the next step.
With the finish you show with fine lines that it is a building of stone.
The second castle is Muiderslot (or Amsterdam castle) in Muiden, North Holland, built around 1285. This castle is more complicated to draw because it lacks clearly structured building layers like the Spanish castle.
Exercise 2: Copy the above view of Muiderslot Castle. Below, I’ll show you how to do this step by step, starting with the tallest tower in the middle of your paper. Build the left and right sides of the castle against it, as if you were playing with blocks. For a pointed roof on a tower, first draw a vertical line through the center (indicated here in red). You can check the right heights with assisting lines (also indicated in red).
EXTRA: maybe you like to look for other castles to draw or fantasize about your own castle, medieval, fairytale or futuristic. Just start somewhere with a tower, a staircase, a building layer or a piece of wall. Wherever you want you build something against or on top of it.