You're sneaking through the Vatican, ducking behind massive Mussolini posters and trying not to get spotted by Blackshirts, when you stumble upon a tiny, perfect marble model of St. Peter's Basilica. It’s tucked away in a room that looks like it hasn't seen a duster since the Renaissance. This is the Indiana Jones and the Great Circle House of God mystery, and honestly, if you aren't looking for it, you’ll walk right past one of the most useful side quests in the early game.
It’s not just about the XP or the "Mystery Solved" notification popping up on your screen. Solving this thing gets you the Vatican Relics exploration book. Without it? You’re basically blind-guessing where the hidden collectibles are across the entire Rome map. Trust me, you want that book.
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Finding the House of God Mystery
Getting to the puzzle is half the battle. You’ll find it in the Apostolic Palace area of the Vatican. Specifically, it's near the Borgia Courtyard. Look for the giant red Mussolini poster—it's hard to miss, given the game's 1937 setting. There’s some scaffolding behind that poster.
Climb it.
You’ll find a window that leads into a hallway filled with statues. The "House of God" isn't a literal building you enter, but a diorama sitting on a chest of drawers. There’s a note on top of it addressed to someone named Ernesto about "cleaning secret compartments." Once you read that note, Indy scribbles in his journal, and the mystery officially begins.
Solving the House of God Puzzle
MachineGames didn't make this a brain-buster, but the first-person perspective can actually make it trickier than it needs to be. You move a lever, something clicks on the other side of the model, and if you aren't looking at the right spot, you’ll think nothing happened.
The First Move: There is a large lever on the front of the diorama. Push it all the way to the right. You’ll hear a mechanical clunk. Look at the left side of the marble model—a small panel has slid open. Inside is a relief medallion. Grab it.
The Switch: Now, take that same lever and slide it all the way to the left. This closes the first panel and opens a different one on the right side of the Basilica model.
The Medallion Placement: Walk over to that open right-side panel. You’ll see a circular indent. Pop the relief medallion you just found into that slot.
The Chalice: As soon as the medallion is in, yet another compartment opens back on the left side (lower down this time). Inside is a Golden Chalice.
The Final Step: Look at the "courtyard" area in the middle of the model, right in front of the church dome. There’s a square pressure plate there. Place the Golden Chalice on that square.
The front of the diorama will slide open like a secret drawer, revealing the Vatican Relics journal.
Why This Mystery Actually Matters
The Great Circle is a game that rewards your inner archeologist, and the House of God is the gatekeeper for that. The book you find doesn't just give you a lore dump; it actually marks relic locations on your map.
In a game where you’re constantly juggling stealth, whip-cracking, and brawling, having a literal treasure map for the Vatican is a godsend. Plus, completing it nets you about 100 Adventure Points (AP). Since AP is what you use to buy upgrades and skills—like being able to survive a fatal blow or making your whip strikes faster—ignoring these "Mysteries" is basically playing the game on hard mode for no reason.
Is It Historically Accurate?
Kinda. The game calls it the "Great Basilica," which is obviously St. Peter’s. The developers at MachineGames have been pretty vocal about wanting to capture the vibe of the Vatican rather than a 1:1 architectural blueprint.
Some players have pointed out weirdness, like finding busts of Emperor Nero or Tarot cards in the heart of the Catholic Church. Historically, the Church wasn't exactly a fan of esoteric stuff like Tarot. But this is Indiana Jones. We're talking about a world where the Ark of the Covenant melts faces and the Holy Grail heals bullet wounds. A puzzle-box version of the Vatican fits the "pulp adventure" tone perfectly.
If you’re stuck or the lever seems jammed, make sure you aren't in "combat mode." The game sometimes prevents interaction with puzzle elements if there are alerted guards nearby. Clear the room, take a breath, and follow the lever.
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To make the most of your time in the Vatican, open your map immediately after picking up the Vatican Relics book. You’ll see new icons for hidden items that were invisible before. Head toward the closest one near the Borgia Tower—it’s usually the easiest one to snag before the plot forces you to move on to Egypt or Sukhothai.