Sketch a design of castle that can be reconstructed fairly easily from construction paper. Base your design off an existing castle, or be creative and design a new one. Be sure the drawing includes the staple architecture from the medieval period.
Grab a shoe box, construction paper, glue stick, scissors and colored pencils. The shoe box will provide the stability for the castle walls. Construction paper will act as a "primer" for the box by allowing the surface to be easily drawn and colored on by the colored pencils. Use the scissors to cut the paper to size and the glue stick to adhere everything together.
Construct the outer walls of the castle by cutting the construction paper to size and gluing it onto the box. Leave about an inch on the top so cutouts can be made to achieve a pattern of 1/2-inch blocks followed by 1/2-inch blocks of space. To make towers, bend the construction paper around the corners and leave a tab where glue can be placed between the box and paper. (This step should be completed first to hide seams.) The towers should be taller than the walls by 2 or 3 inches. To complete the tower, roll the construction paper into a tube and glue it to the outside of the tower where it extends over the box. The same pattern may be cut into the top of the tower walls. Place towers at all four corners and fill in the box with construction paper.
Cut windows and doors into the structure. You may use castle pictures for reference. Most castles; however, contain a large, arched main door that was heavily protected by a gate and arched windows, which were thin to discourage archery fire.
Finish up the castle with the colored pencils. Shading with blue, gray and black can give stones the appearance of age and detail. Add colorful coats of arms onto the castle to give it a sense of ownership. Go the extra mile and construct a drawbridge out of Popsicle sticks and use string to lower and raise it.