The Kumbha Mela is a very famous festival in Hindudom centered around the site of prayAga - the legendary place of confluence of three sacred rivers - ga~NgA, yamunA and sarasvatI

ga~NgA and yamunA are of course great mighty rivers that still flow today. sarasvatI is a river that has gone dry, a "mythical" river for some. But obviously a memory carried by the Indo-Aryans of perhaps the river they were once familiar further west.

The "historical" sarasvatI likely flowed in East Rajasthan and Haryana. Not anywhere close to the central gangetic plain where prayAga is located. But the Hindus have transposed the location of that legendary river to the east, as they migrated from their original home in the north west "brahmavarta" to the gangetic plain and beyond in the east.

This habit of hindus of transposing the memory of the ancient homeland to their new habitats is found elsewhere. As is evident from the numerous dakSiNa kAshis and dakSiNa prayAgas that exist in the deep south.

A fascinating case study is the curious migration patterns that associate the toNDaimaNDalam region of TN (area around kA~nci) with the Old Mysore region in Karnataka

Near Mysore, there is a small town named T-Narsipura (where T refers to Tirumukkudal - which in turn refers to the confluence of three rivers - kAveri, kabini and a mythical third river called sphaTika sarovara. A mini Kumbha-mela is organized in this town every 3 years which has been going on for a few decades now. The village is also an important shrI-vaiSNava center and is home to a v large shrI vaiSNava community in the surrounding villages

But what is the origin of this town? It finds a mention in skanda purANa as per wiki, which I haven't verified. But we know skanda purANa has some v late edits even in the late medieval period. So I wouldn't read too much into that.

An interesting fact I discovered through X is that a 5th generation descendant of a very early shrI vaiSNava figure named naDathur ammAL (13th cen) migrated to T-Narasipura perhaps in late 14th cen. naDathur ammAL himself was associated with an agrahAram near kA~nci (likely TirumukkuDal). This place (TirumukkuDal) is a confluence of three rivers! (palar, vegavathi, cheyyar) And is viewed as a triveNi sa~ngam (mu-kuDal). 

So this shrI vaiSNava figure who migrated to Old Mysore likely saw the confluence of kAveri and kabini and perhaps named his settlement tirumukkuDal (recalling his origins near the kAncI sa~ngam). 

Here's an example of a migrant from Tamil country superimposing a sa~Ngam from his place of origin on to his new place of settlement (which also had a similar confluence but only of two not three rivers)

Today this is forgotten, and local Kannadigas have a Sanskritic etymology for tirumukkuDal, which seems odd. To me, it clearly is a Tamil name used by a Tamil settler from kAnci 

Now centuries later, both these places (tirumukkuDal in kAnci and tirumukkuDal in Mysore) have a reputation of being "dakSina-prayAga"