Cloud Tower was Paul's first house in his original Survive and Thrive, and managed to complete it in only three tutorials; Your First House, Doors, Ladders & Stairs, and Windows & Fences.
Cloud Tower is a non-symetrical tower on a mountain made from a mixture of wood and cobblestone. It has four floors, including the roof and murderhole-basement. It makes use of both ladders and stairs, the stairs, at the time, being very difficult to use. It has a basement where items are stored and murder holes are used (which no longer work, due to the improved AI).
The screenshot of the cloud tower and the surrounding structures has been used in the Minecraft Survive and Thrive II tutorials onwards.