The true Amber. The Primal Pattern is located in Primal Amber, and defended by Wixer 2.0.

From Sign of the Unicorn (in Corwin’s voice):

We had come by way of a trail that wound about Kolvir to the south. It was longer but less rugged than the route across the crest. I’d a humor to pamper myself so long as my side protested.

So we bore to the right, moving single file, Random in the lead, Ganelon to the rear. The trail ran gently upward, then cut back down again. The air was cool, and it bore the aromas of verdure and moist earth, a thing quite unusual in that start place, at that altitude. Straying air currents, I reasoned, from the forest far below.

[…] the sun was a fantastic golden ball. It seemed half again its normal size, and its peculiar coloration was unlike anything I remembered having seen before. It did marvelous things to the band of ocean that had come into view above the next rise, and the tints of cloud and sky were indeed singular. I did not halt, though, for the sudden brightness was almost painful.

[…] When I had blinked away the aftereffects of that display I noticed that the vegetation was heavier than I had remembered in this little pocket in the sky. I had thought there were several scrubby trees and some patches of lichen, but there were actually several dozen trees, larger than I recalled, and greener, with a clutch of grasses here and there and a vine or two softening the outlines of the rocks.

[…] Passing through, it seemed that the little hollow was also wider than I recalled it. By the time we had crossed and were ascending once more, I was certain of it.

The trail curved to the left as we entered among the trees. I could see no reason for this deviation from the direct route. We stayed with it, however, and it added to the illusion of distance. After a few moments it swung suddenly to the right again. The prospect on cutting back was peculiar. The trees seemed even taller and were now so dense as to puzzle the eye that sought their penetration. When it turned once more it broadened, and the way was straight for a great distace ahead. Too great, in fact. Our little dell just wasn’t that wide.

[…] And, continuing, all three dimensions seemed to reassert themselves once more. The sun was that great orb of molten gold we had seen earlier. The sky was a deeper blue than that of Amber, and there were no clouds in it. That sea was a matching blue, unspecked by sail or island. I saw no birds, and I heard no sounds other than our own. An enormous silence lay upon this place, this day. In the bowl of my suddenly clear vision, the Pattern at least achieved its disposition upon the surface below. I thought at first that it was inscribed on the rock, but as we dream nearer I saw that it was contained within it - gold-pink swirls, like veining in an exotic marble, natural-seeming despite the obvious purpose to the design.