Set of 10 trapezoid-shaped supporting blocks and 1 keystone block may be used to build unique towers, naturally curving retaining walls, crenellated castle walls, and a real self-standing arch big enough to crawl through. Supporting blocks have a groove on the outside edge to help kids align arch. Included guide provides building ideas, step-by-step arch directions, and history and modern uses of arches. Convenient vinyl storage bag. POWERFUL LEARNING TOOLS: Stacking and arranging blocks stimulates motor development and spatial reasoning. The Archway Engineering Blocks Set also fosters language, social skills, and collaboration - building an arch builds vocabulary and teamwork! BUILD TOWERS, WALLS, AND MORE: Younger kids can use the set of trapezoid-shaped blocks to build unusual towers, naturally curving retaining walls, or add to existing large blocks to make a crenellated castle wall. THE ARCH - AN ENGINEERING CHALLENGE: Older kids will thrive on the engineering challenge of building a real arch, complete with keystone - it'll take teamwork and cooperation. The resulting arch is approximately 48 inches wide x 22 inches high - plenty big enough to crawl through! LIGHTWEIGHT FOAM BLOCKS: Blocks are made of lightweight EVA foam that's super-easy to stack. 10 trapezoid-shaped supporting blocks (7.25 inches x 5.5 inches x 3 inches thick) have outer grooves to help kids align the arch. Keystone block measures 13.5 inches x 7 inches x 3 inches thick. CONVENIENT STORAGE BAG: Sturdy vinyl storage bag keeps all the Archway Engineering Blocks conveniently at hand for your next building challenge. Ages 3 and up.