Fractionally outside my one-mile zone, but I got curious about Saint Vincent's spring, whose last remnants you can see in a defunct drinking fountain on the Portway. Along the way I passed Gyston's cave, sometimes called St Vincent's cave, in the sheer wall of the gorge. It's now accessible by a tunnel from the observatory—I tried it about twenty years ago, I think, and still recall the vertiginous moment of looking down from the protruding balcony and realising that you could see straight through the grille floor to the drop below—but from what I can work out the tunnel is relatively recent. Before the tunnel was dug it was accessible only by access across the cliff face, which must have been even more terrifying.

Wikipedia says:

This cave was first mentioned as being a chapel in the year AD 305 and excavations, in which Romano-British pottery has been found, have revealed that it has been both a holy place and a place of refuge at various times in its history.

A few different sources say that the cave became a hermitage and chapel to St Vincent following Bristol's early trading in Iberian wines; St Vincent of Saragossa is Lisbon's patron saint, and a lot of nearby things bear the name.

I'm not sure where the crossover of Vincent and Ghyston happens, though. On the giants Goram and Vincent (or Ghyston), Wikipedia says:

The name Vincent for one of the giants rests on the fact that at Clifton, at the narrowest point of the Avon Gorge, there was formerly an ancient hermitage and chapel dedicated to St Vincent, at or near the present cave in the cliff-face which bears his name. Another (apparently modern) version of the story calls the Clifton giant Ghyston, which is in fact the name, of obscure origin, for the whole of the cliff-face of the Avon Gorge at least as early as the mid-fifteenth century, in the detailed description of the Bristol area by William Worcestre. The place-name was personified to produce the giant's name. Vincent's Cave is called Ghyston cave or The Giant’s Hole in an article in the July 1837 issue of Felix Farley’s Bristol Journal.

In my research on the original Hot Well House, I've seen quite a few contemporary paintings which state their viewpoint as "from St. Vincent's Rock", so in the 16th century it seems the cliff-face name was typically St Vincent Rock rather than Ghyston's Rock, perhaps.

I am, as you can tell, no historian!

On the way, I also wandered around the base of the popular climbing area, which I think is the site of the old Black Rock quarry.