Build a large medieval stone castle...

Build a large medieval stone castle with a symmetrical layout, tall central keep, multiple round towers, thick outer walls, arched main gate, stone bridge entrance, and layered battlements. Use only stone-based blocks: stone, cobblestone, stone bricks, cracked stone bricks, mossy stone bricks, polished andesite, andesite, smooth stone, slabs, stairs, walls, and stone brick variants. Do not use ores, glow blocks, wood for structure, colorful blocks, glass lighting tricks, or decorative filler blocks. Keep the palette realistic gray medieval stone only with clean block placement, correct gradients, and proper structural detail.