Built during the years 8,354 to 8,387 CA by Revell Iteratus, Sable Tarn Estate, is located 6 pasangs Ta Sardar Vask (south) of the Cosian City of Temos. The Estate's gates are exactly 1 pasang ta sardar vask of the City walls. Consisting of the massive Estate House and numerous other buildings, it's own calm water harbor, forests, shoreline coves, stunning beaches, pathways, beautiful gardens, canals, and vineyards, the estate is a self-sustaining entity in and of itself. The estate grounds are roughly 31 square pasangs, while the vineyards, forest, cliffs and beaches, are roughly 594 square pasangs and cover almost all of the peninsula Ta Sardar Vask of Temos.  At roughly 625 square pasangs, Sable Tarn Estate is the largest single land holding on Cos.

Sable Tarn Estate produces top quality ta'grapes, it's own specialty vintages of ta'wine, quality war and racing tarns (for which the Estate got it's name), superb herlits, bosk steaks, bosk and verr cheeses, tarsks, blacksmith work, seafood, hosts an annual hunt, and has numerous merchant marine trade ships. The Estate maintains it's own fleet that serves as protection to the Estate as well as the Island.

The Estate's current Master, Lucien Iteratus, the Ubar of Cos, is the ninth generation of the Iteratus Family to oversee the Estate's daily business. The other two Iteratus brothers, Daxos and Stelios, before their deaths, resided on the Estate also. It was to be there that they would have raised families.  The Iteratus Family is somewhat of a Cosian Dynasty. Each man of the Family having raised his family there on the Estate and been sworn, life and limb, to the Ubarate.

The massive Estate House encompasses 196,608 square feet of floor space and is composed of a central keep with four immense bastion towers at the corners. The keep also forms part of the front wall of a larger compound with two more large towers. Bases for a possible further two towers are found at the rear, but these were never developed, and remain the same height as the wall. The Estate House features 440 rooms, 365 fireplaces, and 84 staircases. Four rectangular vault hallways on each floor form a cross-shape.

The roofscape of Sable Tarn Estate contrasts with the masses of its masonry and has often been compared with the skyline of a many a Gorean City: it shows eleven kinds of towers and three types of chimneys, without symmetry, framed at the corners by the massive towers. The design parallels are north Koroban. One of the architectural highlights is the spectacular double-helix open staircase that is the centerpiece of the keep. The two helixes ascend the four floors and two sublevels without ever meeting, illuminated from above by a sort of light house at the highest point of the keep. There are suggestions that a famous Builder may have designed the staircase, but this has not been confirmed.

The Estate House also features 128m of façade, more than 800 sculpted columns and an elaborately decorated roof. When Revell Iteratus commissioned the construction of Sable Tarn Estate, he wanted it to look like the skyline of Ar.

Revell spent lavishly to fund the Estate House of Sable Tarn project. In fact, construction alone took more than a quarter of a century. Started in 8354 CA, work was interrupted in 8365 CA when the coffers of the Estate were completely empty, and didn’t resume until 8367CA. From that date on, you could find up to 2,000 workers on the site at any given time. Revell diverted one of Cos' rivers, the Cosson, to run through the canal, emptying into the deep water avenue in front of the House that leads to the harbor. Water from the Cosson also refreshes the Moat that protects two sides of the House. The Estate House, completed in 8387CA, contains 440 rooms, 84 staircases, 365 fireplaces. It also has tarncots to accommodate 1,200 tarns. The main property is surrounded by 34 pasangs of walls which protect more than 31 square pasangs of grounds, the remaining 594 square pasangs consist of vineyards, woods, game reserve, and beaches. The outer wall meets the wall of the Grounds at the Gate approximately one pasang Var of Temos. Both walls are regularly patrolled by a legion of guards who are loyal to the death to the Iteratus Family. Each guard's family has lived on the Estate for generations. This huge Estate covers more ground than all of Ar!

Today, the Estate is the largest private holding on Cos, portions have been set aside as a hunting reserve since 9,995 CA. It is the largest enclosed property on Cos – with over 625 total square pasangs, of which over 300 square pasangs are made up of native forest, but also includes varieties which were planted such as kalana, tur, tem and willow. A 33 pasang wall, the longest on Cos, encompasses the main estate grounds. The wall has six gates corresponding to six beautiful roads that lead to Var to Temos, Kail to the Adiemus Shipyards, Ror to the interior of the Isle, and three others that lead Rim into the Island and toward the gulf that lies where the peninsula that the Estate sits on meets the body of the Island.

People are only allowed to stroll in the klim part of the Estate. Three observation towers have been built for the benefit of visitors wanting to view the tabuk, sleen and wild tarsk, which gather after sunrise and before sunset in search of food.

The diverted Cosson River, flows in front of the Estate House. Channels which feed the Moat were built by Stan Leczinicus. The River was canaled to provide fresh water for the Estate House and some of the upper vineyards.