egio Ima, the "innermost" regio layer, has only four known entrances, through the four pairs of standing stones in the center of Regio Interior. With an eighth magnitude magical aura, Regio Ima is a mystical and somewhat eerie place, covering an oval about 300 paces across and 2000 paces long.

In the very center is a pyramid of closely fitted reddish granite rocks held in a reddish-orange mortar, about five paces high and twelve paces square at the base, with a counter-clockwise ramp around the outside, ascending to a platform about two paces square at the top.  A stone obelisk rises from the center of the platform, carved with patterns of oak leaves and acorns, apples, and nuts.  The top of the obelisk is flat, as if something is intended to be placed there. Surrounding the pyramid are four trilithons of reddish-brown quartz granite, each with a carved stone head surmounting the lintel-stone:

The hill is mostly bare of trees, but the boundary is lined by 333 trees of varying types (alder, apple, ash, aspen, beech, birch, elder, elm, fir, hawthorn, hazel, holly, hornbeam, linden, oak, pine, rowan, walnut, willow, yew), spaced 13 paces apart, encircling the area that would be bounded by the wall on the outer level. Most of the trees have skulls hung from them in various manners, most spiked upon a branch, but some entwined in branches.  The skulls all face the center of the clearing. Beyond this boundary of regularly spaced trees, primeval forest stretches into the distance, and more of the river is visible than in lower levels of the Regio.

Roe deer, rabbits, and various birds occupy the surrounding forest, emerging at various times to feed in the open ground on the hill. These animals arrived in a mysterious fashion in 1252 AD.

In 1246 AD, when the aura in Regio Ima increased to eighth magnitude, magi noticed that the skulls now resembled dessicated human heads with dry, almost mummifed flesh and hair. Those with the Sight also perceived a spiritual/physical duality to the heads, although attempts to communicate with one head did not yield any response. Additionally, a line of recently-planted trees (lemon, orange, almond, fig, and olive), which lines the edge of the space inside the row of 333 trees, was observed to have a similar spiritual/physical duality. Attempts to commune with a tree yielded little result, but Lucas Faber Jerbitonis expressed his amazement at the apparent perfection of the recently grown trees.

To the west of the pyramid, a tall pentagonal tower of gold-veined white marble rises 99 feet into the sky. It is the Sanctum of Praecisus Bonisagi, conjured as a single block of polished white marble, with chambers and features mystically carved out of the stone. The entrance, facing the pyramid, is an arched double doorway with enormous bronze door valves. Narrow balistraria line the walls of the lower two floors, while large balconies project out from the walls on the upper three floors. The stone of the tower glows faintly, only truly noticeable in darkness or shadow. A large dragon, Umbra, is usually coiled atop the battlemented roof, its head sometimes lowered to peer through one of the balconies on the upper floors.

In 1251 AD, Lucas Faber and Danalia transformed the area south of the pyramid. They raised an immense circular embankment, 400 feet across, at the southern end of Regio Ima, just inside the row of fruit trees. The embankment, which rises about two feet above the ground at its lowest point, is perfectly circular, an uncanny geometric feature (identical circular embankments occupy the corresponding area on each of the lower regio layers).

An immense rectangular hedge, 325 feet wide and 650 feet in length, occupies much of the space between the pyramid and the circular embankment. The space within has been leveled and equipped as an immense outdoor laboratory. Floating a few paces above the interior of the hedgework is an immense rock, nearly one million cubic paces in volume, which Danalia and Placida brought from northern Bohemia in 1252 AD. Subsequently, Danalia re-shaped the rock into the nascent form of Arx Caeles, a massive enchanted castle. In the intervening years, Caelius Jerbitonis has sculpted the rock surfaces into a variety of intriguing and decorative forms. A long earthen ramp runs along the eastern side of the rock, meeting with the Ostium across a tempoarary bridge of wooden beams.