The walls are made from solid granite. The fortress lined with armed guards and military personnel.
And the vault-door code requires 10 different people and no one individual knows the whole sequence.
Well, the St. Louis Blues - hockey's current gold standard - can be justifiably called the game's equivalent of Fort Knox.
When Alex Pietrangelo, Ryan O'Reilly and Jordan Binnington and the rest put 'er in lockdown mode, good luck trying to crack their code.
"I thought we played well, to be honest. Really well,'' reasoned Flames' defenceman Travis Hamonic, a fierce third-period comeback against the reigning Stanley Cup champions falling a whisker short, 3-2 in overtime.
"One of our better efforts in a while.
"They play so heavy. A real heavy forechecking team. They chipped a ton of pucks in. I thought our D did a really good job of making breakouts under pressure in the third.
"I thought we did a good job of trying to close in tight in the corners, those quick support plays. You get out clean, you're going to work in their end, right?
"It's tough to get to their net. They've got a pretty big D corps that skates well.
"Playoff style of hockey. Playoff atmosphere. I thought we hung in there and took it to them at times.
"It's frustrating not to close it out but we did a lot of good things tonight."
Video: Brendan Parker recaps the OT setback to the Blues.
Refer to it as a litmus test, measuring stick, barometer of intentions … whatever.
The Flames, foiled in search of a third straight win, may have dropped a point. But they passed an exam.
Down a deuce with only 11 minutes left to salvage things, facing a group playoff battle-tested in holding leads under trying circumstances, they refused to lose hope or buckle under.
The blossoming Matthew Tkachuk, as is becoming his custom, pulled them back, to within one, from the slot, Andrew Mangiapane arranging the truculent left-winger's 10th snipe.
Then credit Hamonic's hustle with the equalizer, after chipping the puck past the super-sized Colton Parayko down the wall inside the St. Louis zone.
The puck pinballed off the side of the net, Blues' Conn Smythe-winning goaltender Bennington had trouble playing the carom and Hamonic, sticking with it rather than peeling back, cashed a backhander at 16:04 of the third.
Ivan Barbashev and O'Reilly had staked the Blues to a 2-0 lead and, predictably, they looked comfortable trying to protect it until the mid-third-period Calgary uprising.
"They know how to check, right? We know how to check,'' said Flames' boss Bill Peters. "There's a little bit of action, some flurries back and forth. Then were probably trying to get it locked down it he third and we found a way to get back in it.
"A hard-fought game, not a lot of free ice, not a lot of room.
"Whoever was managing the puck properly was the team getting rewarded."
Calgary's feisty response was compromised 2:36 into OT, David Perron snapping an all-in-one-motion dart past the customarily-excellent David Rittich a minute into a 4-on-3 powerplay, T.J. Brodie banished to solitary for a hold.
"I mean, we played well,'' sighed Rittich. "But we made some mistakes. On those plays, we have to figure them out. It cost us a couple games in the past and we're still doing that. So we have to be smarter."
Video: CGY Recap: Flames rally in 3rd, fall to Blues in OT
The Blues arrived on a roll, playing to their grinding identity, having won a half-dozen games on the trot.
"You can see why they were Cup champions last year,'' acknowledged Flames' skipper Mark Giordano. "They play the right way, everybody, right throughout the lineup. They're big, strong, competitive. They lean on you and make things hard on you.
"But in the third, as it went along, I thought we gained more and more momentum and we felt pretty good going into OT.
"Then they get that powerplay …
"For sure we can take a lot out of the game but it's tough to fight our way back the way we did and not get the extra one."
The positives on the night, particularly given the opponent and its stellar form, far outweigh any quibbles.
"I think you can learn from games like this,'' summarized Peters. "There were times we spent a little more time in the D-zone than we'd like to, when we weren't clean breaking out. You've gotta be able to break out on your first try against good teams.
"Once you turn it over, they get a line change, all of a sudden they're fresh and you're tired, they wear you out. I thought they did that at times but our guys hung in there.
"I think being at home recently has helped us sharpen up our game.
"We're getting better here, as we go. Lots of things we can work on, tighten up, clean up, but we're headed in the right direction."