Its shape was a deep oval, and our path dropped down to a circular polished base, roughly two yards in diameter.

Glancing behind me I saw that in the closing of the entrance there had been left no trace of it save the steps that led from where that entrance had been--and as I looked these steps _turned_, leaving us isolated upon the circle, only the faceted walls about us--and in each of the gleaming faces the three of us reflected--dimly.

It was as though we were within a diamond egg whose graven angles had been turned _inward_.
But the oval was not perfect; at my right a screen cut it--a screen that gleamed with fugitive, fleeting luminescences--stretching from the side of our standing place up to the tip of the chamber; slightly convex and crisscrossed by millions of fine lines like those upon a spectroscopic plate, but with this difference--that within each line I sensed the presence of multitudes of finer lines, dwindling into infinitude, ultramicroscopic, traced by some instrument compared to whose delicacy our finest tool would be as a crowbar to the needle of a micrometer.
A foot or two from it stood something like the standee of a compass, bearing, like it a cradled dial under whose crystal ran concentric rings of prisoned, lambent vapours, faintly blue.

From the edge of the dial jutted a little shelf of crystal, a keyboard, in which were cut eight small cups.
Within these cups the handmaiden placed her tapering fingers.

She gazed down upon the disk; pressed a digit--and the screen behind us slipped noiselessly into another angle.
"Put your arm around my waist, Larry, darlin', and stand close," she murmured.