But in this case I tried to make it slightly different by using a real perspective instead of isometric (or axonometric) view, which is most often used for such illusions, and higher field of view showing areas both below and above the horizon (so we see the lower part of the castle from above and the higher part from below). This was quite challenging, because the principle of the Penrose triangle doesn't really work around the horizon. You may notice that both in the lower and in the upper part of the picture there are numerous bridges between the towers, meeting and intersecting in some crazy ways, but there are not so many around the centre of the picture. That's just because the same principle wouldn't work there. But still I hope I managed to make it interesting.