Also in advance: Make buildings. Tint fondant: 18 oz. dark gray, 30 oz. light gray. Add 1/4 teaspoon Gum-Tex to dark gray, 1 teaspoon to light gray. Roll out 1/8 in. thick as needed. Use patterns to cut 2 dark gray small buildings, 2 light gray large buildings. Let dry on cornstarchdusted boards. Using royal icing and tip 2, pipe building details; outline and fill in windows (smooth with fingertip dipped in cornstarch.