Ur-Hekal was a demon city built on a massive volcano.
Along the black ground that was still exuding high temperatures and thick, toxic smoke, a wide magma river slowly flowed along the mountainside. This river seemed to have been deliberately guided, forming rings that circled the entire mountain. In the slowly moving magma, bubbles would burst from time to time, as though the magma in this river would never cool down.
The various buildings built in the demon city completely covered the top of the entire mountain, extending upward in the form of terraces. Although this three-dimensional construction method did not seem large, its volume was quite big.