Human: Write a detailed description of a dreary scene inside a tunnel cavern with a ceiling, mortar, and floor. Assistant: 
Transitioning from packed dirt to smooth stones, the tunnel's floor matches its ceiling and walls, which are curved and stained with watermarks. Thick, grey mortar fills the cracks between the stones, allowing the terrain to be flat and uniform. Condensation at the center of the ceiling either drips with a soft *plink* upon the floor, or runs down the sides of the walls to pool in tiny rivulets that flow eastward.