At this point it becomes more of a source for inspiration for ancient magic than a summae...
Didn't we agree previous one realm level away we can enter our own realm via arcane connection teleport?
Also I didn't say there is no normal way back just without the lvl. 20 Intellego-Vim spell and a to low Vim+Intellego score Paulos didn't discover it trough his visit.
I think I keep the base idea that it is in a divine aligned sub regio of our own regio and the general idea how this great works is working (after all the combination of Intellego, Mentem and Imaginem would result in something like this) but complete drop the time difference of the regio, no food, no drink, no sleep thing.
Yes I will buy it as Suma and Tractatus and it works exact like them if you study it for one or more season (except that i.e. Book learner not apply).
Discovered so far is that it work as (?Holy) Intellego Suma undiscovered that it also works as (?Holy) Imaginem Suma and Mentem Tractatus.
Yes because its a relict of the Grigori it might be a source to gain the minor hermetic virtue Barquijal & Kokabel legacy what allow Intellego, Mentem and Imaginem Vis to handled interchangeably.
I personal won't hand out a way to control the scenes of the past shown and so I don't see it as source to study other Ancient magic and the Grigori Magic sound like it is close enough to the modern hermetic based holy magic that there shouldn't be a issue as well.
(if a other group member want to hand out the control as adventure reward I have nothing against it but the fallout will be his to handle then)
A main question we still have to face if it works full quality for normal Hermetic magic as well or only half.
A divine sub-regio of a magic regio? Not exactly RAW... which keeps these separated.
We may well have. It's entirely possible that I missed that.
My concern is that I don't want the regio to become a potential trap. Even if there is a way out, if it requires resources that may not be in the regio (e.g., a high Art value that a magus may not have) then it may be come a de facto trap. I just don't want the chance for a visiting magus to go see the great work and not be able to get out. That feature seems like something that goes beyond the payment for a summa.
I agree with silveroak. I've never heard of mixing and matching regio types within the levels of the same regio. In other words, I'm not sure how you get a divine regio level in a magic regio. That seems extremely odd, at the very least, an impossible at the most.
Sounds good to me.
That's a good question. My inclination is that if it's bought as a summa/great work then it should follow the same limitations as a summa/great work would, meaning that it would have to be limited to holy magic. But I'm more than willing to be convinced that I'm wrong. 
Hmm ok my thought, was that because of the divine aura of the relict the sub regio was created and the divine aura is the same strength or stronger then the magic aura in this place (i.e. both 2 or 3)
But if you say thats not possible in RAW or a divine aura from a relict that can't be moved need to be bought I have no problem to change it. After all it is just a minor flavor I added because the Grigori where angel.
(Having it to have a Divine aura could also the reason why it was only discovered by accident and not when we used "Piercing The Magic Veil" in our regio what I suppose some mage have done so in the past)
I plan to keep it simple with a pure physical or mental action (the later might be linked to a concentration roll) but you have to know it first and at last from my understanding of regios they are actual supposed to be a trap till you learn what the exit is.
One general way to learn the exits of a magic Regio is the Magic variant of Pircing The Faerie Veil or Second Sight
How are our pre game Lab Texts coming along? Can I get a Holy Magic Re Co 35 The leap of Homecoming or is this to high in level/ all points used? (Can't find the discussion we had about the max level for pre game Lab text again)
It seems like you are trying to get way more than a book for the cost of a book- extra regios of different realms, relics, etc. A Great Work is a book in the form of a building, not a major artifact or a tether of a relic. It could be a cathedral in the city that is under the control of the covenant, but the rest of this is making it into something else entirely. Given that the Grigori straddled the lines of magic and divine I could see Great Work being part of the bronze age settlement in the regio, but it would be in the magic aura, not a divine one, and certainly would not possess any supernatural elements. It would also need to be a "book" specifically on Grigori magic, not something where we are slipping in freebies on the down low.
Anything up to level 40 is ok. Anything above that is ok if a couple of other players agree.
That works for me.