[1] In 1776, it was announced that "the Commissioners for continuing the circular road have marked out its course from Island Bridge to the North Wall, where it will conclude with a horse ferry".

[2] The road is considered as a marker to separate the city centre from the inner suburbs, and runs from the Phoenix Park in the west through Phibsboro, to North Wall in the east.

In the west the R101 connects the NCR to Parkgate Street via the short Infirmary Road ; at the eastern end the R101 becomes Portland Row after the junction with Summerhill.

It continues the northern loop through Saville Place , then turns east for its final kilometre via Sheriff Street (Upper) before terminating at North Wall Road (the R131).

[5] It was leased to a number of tenants, including the Department of Justice, Special Olympics Ireland, the Northern Area Health Board and the Mirror Group.