The yatra is named for three things - Kashi, Ayodhya and the Sangam - and of the three, the Sangam is the one that is less a place to see than an act to perform. The snan, the holy dip at the Triveni Sangam, is the ritual heart of this journey, and it is worth understanding what it means before you stand in the water.
The Sangam is the confluence of three rivers - the Ganga, the Yamuna, and the Saraswati, which flows unseen beneath the other two. To bathe at the exact point where they meet is held, in the Hindu tradition, to wash away sin and settle the soul as nothing else can; it is why the largest of all gatherings, the Kumbh, happens here, and why pilgrims have come to this spot for thousands of years. A dip at Prayag is not sightseeing. It is a sankalp, a vow and a cleansing, taken in the middle of the river.
And there is a rightness in where it falls in this particular yatra - in the middle. You come to it from Kashi, the city of Shiva and of endings, where you have sought the grace of the lord of liberation. You go on from it to Ayodhya, the city of Rama, where you will stand before the divine as devotion made flesh. And between the two, at the Sangam, you are washed clean - the purification that readies you for the darshan to come. Kashi, then the cleansing waters, then Rama: the three move in a deliberate order, and the snan is the hinge on which the whole yatra turns.
A word on how the snan is actually done, since many first-timers are unsure. The boat carries you out from the ghat to the line on the water where the paler Ganga and the deeper Yamuna visibly meet; there the boatman holds steady, and you step down into waist-deep water from the boat itself, or bathe from a wooden platform anchored at the spot. A priest can be arranged to perform a short sankalp - a statement of intention and a few verses - before the dip, and many pilgrims carry a little of the Sangam water home in a sealed pot afterwards, as is the custom. It is gentle, it is optional, and it need take only a few minutes.
Experience My India pre-arranges an authorised boat so the dip is done in peace rather than haggled for on the ghat, keeps your belongings safe in the car, and gives you the quiet minutes at the confluence that the moment deserves. For many who make this trip, the few cold seconds in the water where the rivers meet are the ones they remember longest. Har Har Mahadev, Jai Gange, Jai Shri Ram.