The Caledonian Road passes for about a mile and a half north-south through the London Borough of Islington. It connects North London, from Camden Road near its junction with Holloway Road, and central London's Pentonville Road in the south. It is known colloquially as the "Cally" and forms the entirety of the A5203.
The road is mostly residential from Camden Road until it reaches Caledonian Road tube station. Residential developments have been constructed around the station including student accommodation. South of the station near the bridge carrying the North London Line is Pentonville Prison. South of the prison the road is lined with shops and cafes including several Ethiopian restaurants. The area is poor compared to the north end and the shops serve the council estates bordering the road and the more affluent Barnsbury area of mostly Georgian terraces to the east. The road crosses the Regents Canal at Thornhill Bridge and to the south are trendy shops and restaurants that have opened as a result of the King's Cross Central developments. The road ends at Pentonville Road near King's Cross railway station and the border with Camden. Housmans Bookshop, specialist radical book and magazine retailers established in 1945, is at No.5, as are the offices of Peace News and London Greenpeace, the people behind the McLibel Trial.