

There were many hypotheses that tried to explain Sigil's location and existence. Although all magic was completely impeded at the center of the Outlands, it worked normally within Sigil, with the exception of spells that involved planar travel. The city's location and geometry was considered by most sages, in particular the inhabitants of the Material Plane, to be impossible. Ī view of the Spire and Sigil from the Outlands.

Despite these attempts at measurement, the city did not have a fixed size and its dimensions could be changed at will by the Lady of Pain.

Later measurements put the primary diameter at approximately 6.4 miles (10 kilometers), with the same circumference as the Harmonium's measurements, and a secondary diameter―the ring's thickness―of approximately 1.5 miles (2.4 kilometers). According to official measurements by the Harmonium, the city's primary diameter―that is, the ring's diameter―was 5 miles (8 kilometers), with a circumference of 20 miles (32 kilometers). Sigil was shaped like the inside of a torus. From the Outlands, it was possible to see Sigil hovering atop the Spire as the mountaintop vanished into nothingness. Sigil was located in the Outlands, hovering above the immensely tall landmark known as the Spire that stood at the plane's center.
