So you’re in a tunnel… ”We’ll go forwards!” //
After a while the tunnel opens up into a cave. ”Cool! What’s in there?” //
The cave is very large and high. There’s a little river in the middle of it. The river comes from your left side and… //
”…or wait, I’ll draw it.” //
”So the river comes from here and goes here. The cave is here…” //
”And, weirdly enough, the cave is just the shape to fit onto an A4 sized paper!” ”Caves shaped like that are surprisingly common in role playing games.”