Isaiah 22:1:
A prophecy concerning the Valley of Visions...
Rashi:
"the Valley of Visions" - This is Jerusalem, the valley about which most prophecies were prophesied.
Rashi to Taanith 29A:
"Valley of Visions" -- the valley in which they would prophesy... Alternatively, Jerusalem, for all would gaze at her.
Etz Yoseph to Taanith 29A:
In Pethichta 24 of Echah Rabatha it states: "'A prophecy concerning the Valley of Visions' -- the valley about which all the prophets prophesy." (The meaning is that this prophecy was said concerning Jerusalem. She is called "the Valley of Visions" for all the visionaries, i.e. the prophets, prophecy concerning the return of her inhabitants. [The prophet] called her a valley even though it is a mountain to connote derisively, for her inhabitants cast her down with their evil, making her from a mountain into a valley, for she is no longer worthy to be called a mountain, rather, a valley.) "The valley from which all the prophets derive." According to this interpretation, the term "valley" connotes the high quality of the city and its praise, for just as the valley receives rainwater, so is Jerusalem fit to receive the flow of prophecy, for there is the Gate of Heaven and from there comes prophecy to the prophets, for "all the prophets" (i.e. most) derive from her, as R' Yochanan said: "Any prophet whose city's name was not specified was a Jerusalemite."
