Draw the mountains with uneven lines behind the building. Add two towers to the top of the roof with rectangles and triangles. Draw two rectangles beneath the towers as shown. Sketch curved lines in the upper rectangle. Draw curved lines on two other towers as shown.
Add a straight vertical line at the top of the tower on the right and to the roof on the left. Block many windows using rectangles and odd-shaped triangles. Add some surface detail to the side of the building with straight horizontal and vertical lines.