Tel-Aruhn stood on the northwestern coast of Auridon, at the place where the lower slopes of the Jerall Mountains descend directly into the sea. The city was built upon the narrow ground between the two: a working harbour at the waterline and a tiered city climbing the lower slopes behind it.
The Aldmer Foundation
Tel-Aruhn was founded in the early Daedric Era as an Aldmer settlement, one of the older cities of the northern coast of Auridon. The founders chose the site for the workable veins of stone and metal that ran through the cliff behind it. The city of those first centuries was built in the Aldmer manner, with ordered streets climbing the slope in terraces, and halls of pale stone on the upper levels.
The Elven Wars
Tel-Aruhn sided with the New Tribunal in the opening of the Elven Wars. The city served through the war as one of the chief supply-cities of the Chimer host on the island.
After the Battle of Mount Ator and the subsequent reordering of the realm, Tel-Aruhn was claimed by Sotha Sil as his seat in Ascalon: the city now had a new harbour, the mountain's resources, the workshops, and a hard working population already accustomed to working at the pace the engineer-magician intended to set.
Sotha Sil's Tenure
Sotha Sil left the surface city largely as he had found it but drove an excavation northward into the body of the Jerall Mountains, and the laboratories, foundries, and workshops in which the real work of his tenure was carried out were built into the mountain itself rather than within the city. Tel-Aruhn became the surface gate to a much larger working.
The visible signature of the inner works was the pipework. Steam vents and metal piping ran out of the cliff face above the city, along the upper terraces, and down toward the harbour, carrying coolant water from the mountain to the sea and venting the exhaust of the foundries above the highest roofs.
The propulsion engines that Numilus would later carry out of the city, and from which the airship of Topal eventually descended, were developed in the inner workshops of Tel-Aruhn under Sotha Sil's direction. The work was shared with Falas under the concordats that sustained the peace between Ascalon and Ulumbra for the whole of the era. The chief exchange of research between the two realms passed through Tel-Aruhn's surface gate.
The Withdrawal and the End of Ascalon
When the Lich-King's plague reached the central settlements of Ascalon, Almalexia withdrew her people from the eastern country and gathered them at Tel-Aruhn. The city held. The depth and defensibility of the mountain works gave Almalexia a position the eastern settlements had not possessed, and the Girdle of Vivec drawn between Lake Lenorv and Lake Amon preserved the western country in which Tel-Aruhn stood. Almalexia remained in the city through the War of the Black Moon that ended the Lich-King's reign, and the chronicles preserve her as having governed the surviving Dunmer of Ascalon from Tel-Aruhn for the duration of that war.
The city has been held since by several peoples in succession, each of which has renamed it; the ruin is now generally known as Tol Eressa, though the last people that inhabited it called it Tong-Rao.