The Broad Stairs, also known as Brown Stairs (due to its distinct brown colour) is a material designed by Dr Maria Montessori. It is made up of 10 brown rectangular stairs of the same length (20cm), differing in breadth and height, from 1cm to 1dm. The largest rectangular prism has a base measuring 10cm and the smallest 1cm. The prisms increase in size progressively: 4 of the first prisms make the second, 9 of the first prisms make the third, and 16 of the first prisms make the fourth. The prisms are arranged next to each other from the largest to the smallest so they resemble a staircase.