Whoops, confused Hajj with Arba’een. I did not know about the latter and I assumed that they were the same. Arba’een is much larger than the Hajj.

That's surprising, Hajj gets a lot more press/prestige it seems. Saudi is a similar sized population as Iraq, that infographic comparison is interesting to say the least:

https://en.wikipedia.org/wiki/List_of_Middle_Eastern_countri... (Iran, not listed, is 81.16M)

The Hajj is a once in a lifetime pilgrimage for most Muslims while the Arba'een is an annual regional event of Shia solidarity. The former is done by a far greater number of unique individuals but the latter can be bigger on an annual basis.

What about the Kumbh Mela known as the worlds largest congregation of pilgrims?

TIL!