"Uh ... Uh. But this mound would have dwarfed twenty termite nests in a valley of giants—all tumbled together and piled up in a skyward direction.
"As near as I could make out the footprints ran right up to the base of the mound, and stopped there.
"Well ... you can be sure I didn't just stand in my own prints goggling up at the stars. I followed that impossible trail—straight out into the valley as fast as I could clump.
"It took me about ten minutes to reach the mound. Once or twice I stumbled and almost went sprawling. But whenever I felt the plain slipping out from under me I shot a quick glance at the mound and its sheer massiveness steadied me.
"Close up it had a corrugated, hoary look, as if it had bubbled up out of the ground when the moon had a molten crust and been fused into a mound by fire and earthquake.
"But when I halted directly in front of it I saw that it wasn't as solid as it looked. It was riddled with little dark holes, as though a woodpecker had spent at least a month making a wreck of it. And at its base there was a wide, dark, tunnel-like opening.
"Another man might have thought of a hundred excuses for not crawling through that tunnel on his hands and knees. But when my curiosity is aroused I'm a very special kind of idiot.
"The tunnel was about twenty feet in length. I crawled along through the darkness with my atomic blaster slapping against my hip, my heart hammering against my ribs.
"When the smothering feeling you get in tunnels began to wear thin I knew that it would be safe for me to stand up. You can feel a stone wall arching above you without touching it, and I knew suddenly that I was in the clear.
"When I got to my feet and stared about me I could see the dark end of the tunnel and what appeared to be stone walls hemming me in. The walls arched away into shadows, and were faintly luminous.