A ziggurat is a type of step pyramid developed by the Sumerians around 3000 to 2500 BCE. The structures acted as temples for the Sumerian gods and they resembled rectangular cuboids placed on top of each other. This simplistic architecture is what makes ziggurats easy to recreate with paper.
Design a 7-by-7-inch square on yellow construction paper. Create rectangles on all four sides of the square, measuring 2-by-7 inches (since one of their sides is actually the square's side). Cut out the whole template.
Fold the template on the square's sides and use tape to hold the rectangles (ziggurat's walls) together. Cut out a small rectangle on one of the walls to form the level's door.
Create an identically shaped template for the second level, with the square measuring 5-by-5 inches and the four rectangles measuring 2-by-5. Cut out the template, fold and stick the walls together and cut out the level's door. Place the new level over the initial one, with the doors facing the same direction.
Repeat the process to create the third level, with a 3-by-3 inch square and 1-by-3 inch rectangles, and the top level, with a 2-by-2 inch square and 2-by-2 rectangles. Cut out the templates, form the walls, create the doors and place them over the bottom two levels.
Measure each level's wall height and the door's width. Create a trapezoid for each level except for the top level, whose bottom side equals twice the height + the door's width, while its top side equals the door's width. Each trapezoid's height must equal the distance between the walls and the edge of the lower square (not applicable for the bottom level's trapezoid, whose height should be twice the wall's height).
Draw two orthogonal lines, starting from the trapezoid's top side corners and reaching the bottom side. Fold the shape on these two lines to form each level's ladder. Stick the ladder right in front of each level's door (effectively covering it).
If you cannot find a yellow construction paper, paint the paper yellow or orange to give the impression of mud (the main material used for the construction of ziggurats).