First cut out base of the building, fold and glue into a square box shape.

Next cut out the walls of the inner section of the base. Note that the two folds at the center of this piece are reverse (valley) folds, so that the piece will be folded into a "U" shape with the printing on the inside. The two tabs at the back of the piece are reverse folds as well. Score and fold the back tabs inward, and the three tabs at the front of the piece backward.

Test to make sure the U-shaped inner wall fits correctly first, then glue it in place inside the base. The tops of the inner wall will stick up above the roof of the base, while the three front tabs will be glued behind the clock and front wall of the base.

Cut out the tower. Score all the fold lines carefully. Assemble the tower into a rectangular box.

Fold the four tabs on the inner part of the tower back at a 90-degree angle using a tweezer to make a sharp crease and straight fold.

Fold the two sections of roof down horizontally.

Test fit to make sure the two boxes fit smoothly inside the slots of the tower. You can push the inner tabs of the tower back farther with a tweezer to give more room if necessary.

Glue the boxes into the slots of the tower (with the cut-out part facing the front). Then slide the long side of the tower into the inner section of the base. Match up the window levels of the tower, the two boxes, and the inner section of the base. Reach inside the base to push the tabs of the inner section against the back of the long side of the tower to glue in place.

Cut out pyramidal roof of the tower. Carefully score the tiny fold lines and fold with a tweezer to get a crisp edge. Fold the bottom of the pyramid into an octagonal box with corners at 45-degree angles.

Fold the long, squat sides of the roof inward and then glue the thinner, tall roof sides down to the tabs.

Cut out the tiny statue of Ceres and glue it front to back. Glue the statue at the apex of the pyramidal roof. After the glue dries you can reinforce the tiny statue with a bit of super glue touched to the edge of the paper, as described in Tips & Techniques.

Cut out the four smaller steps of the tower. Score them carefully and fold into rectangular shapes. Note that one side of each piece is slightly longer than the other. These pieces will be glued at the corners of the tower, with the longer edge overlapping the corner.

Lastly, cut out the two mechanical sheds and assemble into rectangular boxes. Glue them to the roof on each side of the inner section.

Now your Chicago Board of Trade Building is finished!