Randall:

”Indeed, let us breach the wall with a small hole at first.  I suspect it may be the result of a Wall of Stone spell,” replies Randall.

"If its keeping something in," he leaves that thought hanging. "Shame, we can't see thru walls, if worse comes to worse,  I can punch thru." He holds up the hand, sporting the ring of the ram. 

"Indeed, I think that's a good idea. Let me try to have a look!" Zenodor walks up to the thin wall and mutters an arcane incantation in a strange tongue. He gains the ability to see through solid objects (and walls) and has a look to see what's on the other side. (He will also look around in all other directions in case there's something else of interest behind one of the other walls.

Skill: Ghostly Gaze

Once per short rest, as an action, you gain the ability to see through solid objects (with darkvision) to a range of 30 ft for 1 minute

You can see part of the room, which contains several small chests resting atop piles of coins, but it is bigger than 30 feet so the far reaches remain unseen.

"I cannot see the whole room. There are some chests and piles of coins directly on the other side of the wall, but the room is much deeper than my magic can penetrate.

But at least there is nothing waiting immediately on the other side. Perhaps we should make a small hole next, as Randall suggested.

(Now that Z has seen the room, could he use Scrying to get a sensor into it and see the rest?)

Scrying can only target creatures.

Quote from Brian_Avery >>

Scrying can only target creatures.

https://www.dndbeyond.com/spells/2619007-scrying : "... Instead of targeting a creature, you can target a location you have seen. When you do so, the sensor appears at that location and doesn’t move."

Quote from Touschka_ >>

Quote from Brian_Avery >>

Scrying can only target creatures.

https://www.dndbeyond.com/spells/2619007-scrying : "... Instead of targeting a creature, you can target a location you have seen. When you do so, the sensor appears at that location and doesn’t move."

[ So my thinking is: Put the sensor 30ft in (as far as he is able to currently see), and from that point he can then see a lot more of the room (120ft dark vision, or further if there is light). So that gives 150ft at least, potentially more. Unless it's a gargantuan cave, that should give a good view.

Or alternative: Arcane Gate? "Choose two points on the ground that you can see, one point within 10 feet of you and one point within 500 feet of you." He can now see the other side of the wall, so we could open a portal that stay open 10mins and which we could close if there's something dangerous on the other side. But on the downside, we could get (temporarily) stuck there if the portal closes]

Sorry, I was in a hurry and didn't read the entire spell... missed that part at the bottom.

You can indeed put the sensor 30 feet in.

It is a square shaped room 80 feet on a side, the ceiling is 40 feet high. There is a finely made double door centered on the far wall and a regular door on the left wall about 15 feet from the far wall. Mounds and mounds of coins with a mix of small chests and a variety of odd items (pieces of art, helms, weapons, shields, small items of furniture) scattered around, some rest atop mounds of coins while others are half buried. You have never seen so much treasure before.

Quote from Brian_Avery >>

Sorry, I was in a hurry and didn't read the entire spell... missed that part at the bottom.

You can indeed put the sensor 30 feet in.

It is a square shaped room 80 feet on a side, the ceiling is 40 feet high. There is a finely made double door centered on the far wall and a regular door on the left wall about 15 feet from the far wall. Mounds and mounds of coins with a mix of small chests and a variety of odd items (pieces of art, helms, weapons, shields, small items of furniture) scattered around, some rest atop mounds of coins while others are half buried. You have never seen so much treasure before.

 Z passes on this information to the rest of the group, and then adds "Looks like a treasure room to me. Perhaps we found the back wall of it? If the wall is thin enough, I suggest we break into it ... quietly, just in case there is some sort of guardian on the other side of the door."

After thinking for a minute he adds "I could block one of the doors with a Forcecage, perhaps a solid one, if necessary. Does anyone else have a way we could block the other door while we emtpy this treasury? As for transport: I can summon a door to a little demi-plane of our own, which would give us a 30ft cube of space ... which would hold a lot of coins and treasure"

"We are here, to destroy an evil, the treasure may be cursed, we should leave it undisturbed." Tempe, simply says. "If they're was only a way to get thru, without making too much noise."

(To be honest, I have completely forgotten why we're here. I guess it's just a standard adventurer thing to do, to take the treasure?)

Zenodor: "It may be, but it could also just be the stolen riches of the people, used to fund an evil scheme. If it is a trap, why would they put so much effort into stopping us from getting to it. Either way though, should we not try to remove it from the evildoers? If it is cursed, we can later empty the demiplane into a volcano or similar. If it is not, imagine the good we could do by bringing this back to help rebuild the lives of the people who were wronged."

((@DM do we have any clue how we are currently located in contrast to where we know the temple entrance was?))

You have deviated far from the temple and it's entrance. This is... someplace else.

(How far "else"? We're not accidentally robbing a bank or something?)

No. The temple was discovered in a remote location. It is a rediscovered ancient temple.

This area you are exploring is separate from that and even older.

"Let's get through the wall than and see what is here." Pepin says and if noone stops him he'll start working the wall with his warhammer.

"Seems, fitting, being lead to a hoard fit for a dragon, after fighting dragons that control goblins, from a black tent, and dracoliches, but what are we up against? That is the question. I heard my kin sit to absorb the essence of metal and magic."   he says as he watches the hammer blow.

((Pepin would use what he thinks works best to get through the wall quickly; so either warhammer (maybe with booming blade) or masons tools.

Is a roll needed?))

Quote from Secretfool >>

((Pepin would use what he thinks works best to get through the wall quickly; so either warhammer (maybe with booming blade) or masons tools.

Is a roll needed?))

( Z has a Crowbar and Hammer in his pack which he is happy to offer, if it's of any help)