If a well recorded by Treharne-James in 1905 was centrally placed within the principia, and a square outline is assumed, then the fort had dimensions of 152 metres (499 ft) across the rampart crests, covering an area of 2.3 hectares (5.7 acres).

The latest pottery recovered is Trajanic, confirming that the site was abandoned in the Hadrianic period, with its garrison, moved to a new build fort at Gelligaer.

[3] Developed on a site opposite the works, but "sufficiently removed from the town by the extent of the pleasure grounds, and contains all the conveniences and the luxuries requisite for a family of wealth and importance," Homfray was waited on by servants who were dressed in a scarlet and buff livery, while he was driven everywhere in a coach and four horses.

Amid great interest from the public, on 21 February 1804 it successfully carried 11.24 tons of coal,[8] five wagons and 70 men over the full distance, in 4 hours and 5 minutes, at an average speed of 2.4 mph (3.9 km/h).

[11] The Penydarren Ironworks had been financed by William Forman of the Tower of London,[12] who provided all the capital, partly on mortgage but also by taking shares himself.

After a protracted struggle in which hundreds sustained an injury, some fatal, the Highlanders were compelled to withdraw to Penydarren House and abandon the town to the rioters.

[3] While the site of the Ironworks was left to decay, eventually becoming the service depot of the Merthyr tramway, from 1870, parts of the estate were sold off for housing development.

In the 1890s, developments included the general hospital, the Roman Catholic Church of St. Mary's, and the imposing Park Terrace and nearby large villas.

The filling in of the former fish pond marked at Bryant's Field allowed the development of Penydarren Park between 1902 and 1905, during which additional excavation of the Roman fort was undertaken by Frank Treharne-James.

By 1910, the Edwardian Baroque YMCA and the Masonic Temple had been completed, and post World War I Penydarren had become Merthyr Tydfil's premier middle-class suburb, with the addition of further terraces north and south of Dane Street, and properties along the Grove.