The slides are snapshots of an unfolding landscape.
Nothing puts the isolated snapshots in context like maps of caves and surface terrain.
Unfortunately, 35mm slides of regular paper maps are often invisible to the audience. They see what appears to be a yellowish wall in someone's house with some cracks in it. The good news is that high quality, color, black-background slides are easy to make. See examples below. The key is combining a computer monitor with a regular 35mm SLR camera, both of which you probably have or can borrow.