The barn was built in 1882 in accordance with a design by Armstrong and is believed to have been built by local craftsmen from area materials.
 It was three stories high, shaped like a "wedding cake," with each floor smaller than the one below it.
The first floor is about 100 feet (30 m) in diameter, the second floor 75 feet (23 m), and the third floor 30 feet (9.1 m).
The barn stands 48 feet (15 m) high from ground level to the top of the ceiling in the third floor.

The foundation was set on stone abutments quarried from rock in a canyon located about five miles (8.0 km) away.
 Armstrong stated they were driven twelve feet below the water table and set on bedrock.
The walls were of wooden planks, made of three thicknesses of lumber deep, said to be insulated with "double sheets of building paper" between each layer of lumber.
The entrance to the barn originally featured an engraved 4-by-8-foot (1.2 by 2.4 m) horse scene placed over the door.

The barn featured a 20-foot (6.1 m) wide, indoor training track with dirt footing, claimed to be “nearly a quarter-mile” in circumference, on the ground floor, where Armstrong's horses were exercised.
 Horses normally kept outside could be sheltered there in bad weather.
 There were 26 box stalls on the first floor, around the outside of the track, with dividing walls only four feet high between the stalls so the horses could see one another, as Armstrong believed that "this promotion of neighborly companionship greatly [relieved] the monotony of indoor horse life."
Each stall included a doorway to the outside and a window.
The doorways led to 26 paddocks, one for each horse, covering 2 ¹⁄₂-acre (1.0 ha).
A circular structure in the center contained the tack room, two hospital stalls, and a spiral stairway.
 There was also an “elevator” for moving hay and grain, and a well shaft was sunk in the center of the barn, which, with the aid of a windmill on a 12-foot (3.7 m) tower at the top of the barn, drew water that was stored in an 11,000-US-gallon (42,000 l) tank on the third floor.
 The first floors also included office space and sleeping quarters for staff.
 The second floor was claimed to hold up to 50 tons of hay and 12,000 bushels of grain.
 The floor sloped and chutes were cut into the floor so that feed could be easily deposited into the mangers of the horse stalls below.
Water from the third floor tank went through a gravity-based plumbing system to each horse's stall.

Charles Armstrong, Noah's son, said the barn "may truly be called a model of architectural beauty and convenience.
 This structure is so novel in its conception, so convenient in its economy, and withal so admirably adapted to the purposes of its creation, that a description of it cannot but be of interest to the readers of this sketch."
The barn was built in 1882 in accordance with a design by Armstrong and is believed to have been built by local craftsmen from area materials.  It was three stories high, shaped like a "wedding cake," with each floor smaller than the one below it. The first floor is about 100 feet (30 m) in diameter, the second floor 75 feet (23 m), and the third floor 30 feet (9.1 m). The barn stands 48 feet (15 m) high from ground level to the top of the ceiling in the third floor.
The foundation was set on stone abutments quarried from rock in a canyon located about five miles (8.0 km) away.  Armstrong stated they were driven twelve feet below the water table and set on bedrock. The walls were of wooden planks, made of three thicknesses of lumber deep, said to be insulated with "double sheets of building paper" between each layer of lumber. The entrance to the barn originally featured an engraved 4-by-8-foot (1.2 by 2.4 m) horse scene placed over the door.
The barn featured a 20-foot (6.1 m) wide, indoor training track with dirt footing, claimed to be “nearly a quarter-mile” in circumference, on the ground floor, where Armstrong's horses were exercised.  Horses normally kept outside could be sheltered there in bad weather.  There were 26 box stalls on the first floor, around the outside of the track, with dividing walls only four feet high between the stalls so the horses could see one another, as Armstrong believed that "this promotion of neighborly companionship greatly [relieved] the monotony of indoor horse life." Each stall included a doorway to the outside and a window. The doorways led to 26 paddocks, one for each horse, covering 2 ¹⁄₂-acre (1.0 ha). A circular structure in the center contained the tack room, two hospital stalls, and a spiral stairway.  There was also an “elevator” for moving hay and grain, and a well shaft was sunk in the center of the barn, which, with the aid of a windmill on a 12-foot (3.7 m) tower at the top of the barn, drew water that was stored in an 11,000-US-gallon (42,000 l) tank on the third floor.  The first floors also included office space and sleeping quarters for staff.  The second floor was claimed to hold up to 50 tons of hay and 12,000 bushels of grain.  The floor sloped and chutes were cut into the floor so that feed could be easily deposited into the mangers of the horse stalls below. Water from the third floor tank went through a gravity-based plumbing system to each horse's stall.
Charles Armstrong, Noah's son, said the barn "may truly be called a model of architectural beauty and convenience.  This structure is so novel in its conception, so convenient in its economy, and withal so admirably adapted to the purposes of its creation, that a description of it cannot but be of interest to the readers of this sketch."
Doncaster Round Barn