Yes they do, I'm looking at one right now.
Round walls were harder to knock down than right angled walls. If you hit a round wall not much damaged would be made but a right angled wall would cave in.
Animals do not have cell walls, animals cells with cell walls do not exist.
Cell walls only exist in plants.
Castle (or other walls) are called concentric if they form a series of (very roughly) cirular walls round one centre. By the late Middle Ages major castles in Europe often had three walls round a central keep.
Round house walls were typically made of materials such as wood, stone, clay, thatch, or a combination of these materials. The choice of material depended on the region where the round house was constructed and the availability of local resources.
Your grammar is atrocious.
Then life would not exist.
Round the Twist - 1989 If the Walls Could Talk 3-12 is rated/received certificates of: Australia:G
in a word no
Level 15 walls do not exist in Clash of Clans, although they might in a future update.
chair legs and round surfaces such as table legs. round wooden surfaces
yes, south of old walls of rome.