Sure thing! Start by using double‑layered cardboard for the walls—fold the layers in opposite directions so the joints lock together. Add a lattice of small cardboard strips inside each wall for cross‑bracing; that gives the shape some rigidity without adding weight. For the roof, cut a triangle from a single sheet and reinforce the corners with thin cardboard ribs, then tape the edges to the walls. Keep the castle low to the ground so the wind hits less surface area. Finally, seal all seams with a quick‑dry glue and a light coat of waterproof spray to keep the structure from rattling in the breeze. It’ll look clean, stay strong, and still feel like a little marble sculpture made of cardboard.