Ziyarat is visitation to the graves of the family of the Prophet and the imams, and although it is not one road it functions as a circuit with a fixed geography and a fixed text.
What the visitor does
The visit is not looking. Ziyarat has a liturgy, fixed texts recited at the threshold and at the grave, among them Ziyarat Ashura and Ziyarat al-Warith, so the visit is an act of speech performed in a set order. The geography runs through the Atabat of Iraq, Najaf for Ali, Karbala for Husayn, Kadhimiya and Samarra, and through Mashhad and Qom in Iran, with the shrine cities doubling as central seats of Shia learning.
The contested part
Building over graves and seeking intercession there is rejected in Wahhabi and much Salafi doctrine as innovation bordering on shirk, and that reasoning lies behind the demolition of the mausolea of the Baqi cemetery in Medina in 1806 and again in the 1920s, which is now a permanent part of what ziyarat means to those who make it. The bombing of the Samarra shrine in 2006 destroyed the golden dome and triggered the worst phase of the Iraqi civil war. The circuit is at once a devotion, a scripted liturgy, and a live sectarian fault line.