This painting was used as a visual at an April 1988 Houston-hosted conference titled 'Lunar Bases and Space Strategies of the 21st Century.' Here, a surface exploration crew begins its investigation of a typical, small lava tunnel, to determine if it could serve as a natural shelter for the habitation modules of a Lunar Base. One member of the expedition is standing on the lip of the rille near the point where the original tunnel disgorged its lava into an open channel. The two crew members in the foreground are standing in the lava channel. As indicated by the lack of meteorite erosion and debris burial, a section of the original tunnel's roof collapses sometime in the relatively recent past, perhaps due to the impact which formed the l5-meter diameter crater behind the crew member at the rille's edge. The collapse of this section of the tunnel roof exposed the layering in the volcanic rocks and displaced the mouth of the tunnel some 50 meters upstream of its original position.