"About twenty minutes ago. We must be a mile below the ice by now."
So M'Tonak lay somewhere beneath the Polar Cap! That was why men in ages past had been unable to find it, until it became a legend on a par with Earth's lost Atlantis! Jim tensed in his seat now as he thought of all the conflicting reports he had heard about M'Tonak; vague questions crossed his mind to which there were only vaguer answers.
Now the passage through which they sped seemed to widen. Simultaneously they were in a sea of softly diffused, pale greenish light. This light increased as they went on, but did not become intense or glaring; rather it seemed to permeate the very atmosphere from some subtle, unknown source. Then, with breath-taking suddenness they burst out into a vast open place and looked upon the city of M'Tonak.
M'Tonak lay in the center of a vast, shallow bowl several miles wide. In the first start of amazement Jim thought they must have somehow emerged again upon the planet's surface; but this thought was immediately discarded when he gazed across at the opposite horizon. It was concave rather than convex, which meant they were in a cavern of inconceivable dimensions. Far overhead he saw something vague and misty that must have been a roof. That soothing green light was everywhere but he still could not determine its source, it simply seemed to exist.
Now they were gliding gently down into the city which consisted of low-structured, white-marble buildings of peculiar architecture. Wide, empty avenues stretched away in a perfect geometric pattern.
"This city must be inconceivably old!" Conley gasped. "There's no other architecture like this anywhere on Mars!"
Their car was slowing now. It came to rest in a wide circular plaza. The door slid smoothly, invitingly open.
Jim glanced at the others who made no move to leave. He didn't blame them for not moving, for there was something strange and devilishly pre-arranged about all this.
"End of the line!" he said with a jocularity he did not feel. He moved to the door and stepped out.
Instantly he was aware of a strange difference. It might have been that alien green-tinged atmosphere, as if he had suddenly stepped into another dimension. Every fiber of his being now seemed to tingle in a peculiarly delightful way. It was very slight, scarcely felt, but there was no mistaking it.