Does anyone know?

[Billy]

I didn't know you could bring down a wall by shouting the word 'children'- I'll have to try that sometime!

(It's Jericho, not Jerico, by the way)

[Raven]

Thanks, though I don't know how many children would know about the walls of jericho, I sense a little 'warning team' hint being used.

[Golgarach]

I think it was Chris and chums (who got stoned by Medusa) who blew the wall down at first.

[Billy]

Correct!

[Thanatos]

Billy, it seems, is not privy to the mysteries of the inverted comma.

[Dan]

maybe some member more technical than I would be obliaging and put in a link to them

Tada:

[MoanaLiza]

And also t6s1

and t3s2

[Purgatory]

didn't we see this in s3 once??

[HStorm]

No. This room itself was Merlin's only access point in level 3, and it was used in all of the first three seasons, which is why you recognise it from s3, but the wall of Jericho never appeared after s2.

[MoanaLiza]

This is the one from series 3 as we see minus the wall and minus the steps. The rest of the room is unchanged though.