There is a big wall that I've found twice. I think it's unusual. Is it a bug or a sign for something?

I have found a big wall twice. One in the desert made of sandstone and dead bushes, and one of grass. We also found three unusual villages in the same world. I think I also found a +Wither Skull+in a villager's house as well as a tree in the middle, and a hole to a cave in a lookout tower!Is this a bug, a sign for something or am I being weird and they're normal things? Please tell me!