If this is a Russian nest of spies, as Ukraine's government is suggesting, there could not be a more magnificent and grandiose place for alleged agents to hide.
Within the walls of this extraordinary 1,000-year-old complex, which includes a monastery, crypts, chapels and a labyrinth of subterranean caves, a brutal political game is playing out.
The Pechersk Lavra in Ukraine's capital, Kyiv — often referred to simply as the Lavra — is at the centre of a bitter political dispute running parallel to the nation's war with Russia.
The fight over the Lavra reflects deepening tensions across Ukraine.
Ukraine's church was under the jurisdiction of the Moscow patriarchate for three centuries.
But a schism developed within the Ukrainian church between those loyal to Russia and those who wanted to be independent.
In 2019, they were allowed to split, and the names the churches gave themselves were subtly different — but their allegiances are not.
The Ukrainians refer to their church as the Orthodox Church of Ukraine (UOC), whereas the Russian part calls itself the Ukrainian Orthodox Church of the Moscow Patriarchate (UOC-MP).
These factions of the broader Orthodox church co-existed, sometimes uneasily, on this compound.
But due to the tensions unleashed by the war between Russia and Ukraine, often-subterranean tensions at one of Europe's oldest and most famous churches have broken into the open.
Ukraine fears 'Russian saboteurs dressed as priests'
For years, one of the Russian-linked leaders at the Lavra, the Metropolitan Pavel, has held a prominent position, even though Ukrainian intelligence, in recent times at least, has made allegations against him.
The country's intelligence agency, the SBU, insists some members of UOC-MP, including Metropolitan Pavel, have maintained close ties with Moscow.
Authorities claim he has glorified Russia's invasion of Ukraine.
They have now placed the Metropolitan Pavel under house arrest, attaching an electronic tag to his leg.
"I haven't done anything. I believe this is a political order," the religious leader told reporters after the ruling.
He also complained that the living conditions at his home were not fit for him to be under house arrest for 60 days.
"There is nothing to sleep on, no heat and no light. There is no kitchen, no spoon. But it's OK, I'll endure it all," he said.
He has also been banned from recording addresses to his followers.
His arrest follows a raid on the Lavra last year by SBU agents who said they were investigating reports the site was used "to hide sabotage and intelligence groups, foreign citizens, [and store] weapons".
And last week, Kyiv exchanged a priest accused of collaborating with Russia for 28 Ukrainian soldiers.
The prisoner swap is a public indication of the value that Russia places on these priests in Ukraine.
"A lot of priests became collaborators," said Andrii Kovalov, a leading academic on the Lavra who joined the Ukrainian army last year.
"They have actively supported the Russian army by informing Russian artillery and aviation.
"That's why the [Ukrainian] government has started to act against Russian saboteurs dressed as priests."
While many of these tensions have been below the surface, they are now being spoken about openly.
"Russia is our bad daughter," Mr Kovalov said.
"And now our bad daughter is trying to fight its mother."
How Russia uses religion as 'soft power'
Mr Kovalov did his PhD on the relationship between religion and security in Ukraine and has been working as a political and religious analyst since 2010.
He argued that Russia had been using religion as "a soft power" to influence and infiltrate Ukraine.
That was why Ukraine came to the point, he said, of realising that it needed to have an independent church – and hence the recent crackdown against alleged Russian influences.
The war, he said, had been a catalyst for these tensions coming to the surface.
"Before, the Russian church was masked under the cover of the Ukrainian church," he said.
"But the war made the differences very clear and explained to the average Ukrainian who was not interested in politics that the [UOC] is the only legal church which cares about the Ukrainian people and prays for the Ukraine nation and soldiers."
It was obvious, he argued, that there had been people at a senior level of the Lavra who had been supporting Russia and its invasion of Ukraine.
He said that in a time of war, it was unsustainable for there to be people at the head of a venerable religious institution supporting the invasion of the country in which they were being hosted.
He stressed that not all Russian priests at the Lavra were Kremlin sympathisers, but in such a sensitive time of war, one supporter or "collaborator" was too many.
He argued that when Ukraine was fighting for its existence, no such support could be tolerated.
"The Russian Federation [for] thousands of years was trying to absorb Ukraine," he said.
"Russia has stolen our history, our traditions, and Russia never imagined its history and civilisation without Ukraine.
"When [Vladimir] Putin says that Russia and Ukraine are the one nation, he's in fact crossing out the right of Ukraine to exist."
As tensions rage inside the Lavra, war continues above ground
Tensions between the Russian and Ukrainian elements of the Orthodox Church have existed for centuries — the Lavra itself reflects the two streams of the church.
Paintings or images of Ukrainian heroes sit nearby a portrait of Metropolitan Pavel.
"The Lavra for centuries was like a major historical and religious site for [the] orthodox church in Ukraine," Ukraine's Minister for Culture and Information Policy Oleksandr Tkachenko told the ABC.
"It's one of the biggest monasteries, which by origin comes from the 12th or 11th century … its importance from a historical and religious point of view is huge."
Mr Tkachenko said the UOC-MP had been behaving inappropriately during the war – including a refusal by some in that branch to recognise the territorial integrity of Ukraine.
He said the accusations against the Metropolitan Pavel were now a matter of the courts.
"Each of these cases needs to be proven by the secret service or police," he said.
"There are a lot of cases that are now under investigation, with accusations of collaboration, with accusations of not recognising the territorial integrity of [the] Ukrainian state by representatives of the Russian church."
Mr Tkachenko said photographs of such a senior church figure as the Metropolitan with an electronic tag around his leg would have been confronting to many people.
But he did not express sympathy for his claims of hardship.
"He was, for many years, moving, not with this thing [around his ankle], but in a Mercedes car. So he used to know how to live a lucrative life," he said.
Asked about the view of some Ukrainians that the church had become a nest of spies, Mr Tkachenko said there was evidence of collaboration and misinformation.
"Unfortunately during the war, many cases happened where representatives of the [UOC-MP] were directly collaborative with Russian troops, or were provoking their believers … and spreading disinformation," he said.
"So as a machine of mass media, the Kremlin is using [the church] as a propagandistic machine tool in the war."
Mr Tkachenko said the question of loyalty within Ukraine's churches was not about freedom of speech and freedom of religion.
"This is a question to Russia, not for Ukraine," Mr Tkachenko said.
"In Ukraine there are a lot of different representatives of religious organisations – Jewish, Muslim, Protestants, Greek Catholics and so on. It was always a sort of dialogue between them, a sort of consensus on how to act."
And so while a political battle of sorts rages inside the Lavra, the rest of Ukraine continues its war with Russia.
"If you ask ordinary Ukrainians, 95 or 97 per cent of them will respond that they believe this war should be finished as soon as possible, but with only one caveat: victory for Ukraine," he said.
