Pull off several large pieces of clay in roughly equal quantities. Roll these between your hands to make long, thick lengths of clay.
Grab one of the clay pieces. Fold it so the center forms a curved top and the two sides come down straight. The curved part serves as the support for the top of the aqueduct, while the straight sections form the support legs. Repeat with the other rolls of clay to create a series of arches. Lay these arches on your work surface with their sides touching.
Push the sides of the arches together so two adjacent arches form one solid wall.
Add small pieces of clay to the space in between two arches so the series has a long, flat top with no gaps.
Stand the series of arches on the legs. If you have trouble balancing the arches, place some clay around the bottom of each leg to provide support and balance.
Build additional arches in the same manner but with smaller pieces of clay. Take this row of arches and carefully place it on top of the larger series to illustrate a classic Roman aqueduct in three dimensions.