A group of volunteers from the southern Ukrainian port city of Odesa have taken their fight to save lives underground into one of the world's largest labyrinths of catacombs.
Descending more than 20 metres deep into the dark, forgotten tunnels, the group has been working to turn sections of the tunnels into liveable bomb shelters.
Before the war, 32-year-old electrical engineer and blogger, Roman Mauser, explored and made videos of the catacombs.
Now, as the city faces increased attacks by Russian forces, he is using his knowledge to "save lives".
"On the night [of February 24], the first rocket hit Odesa and almost every day [now] we have air-raid alerts," Mr Mauser told the ABC.
Over the past month, Russian missiles have struck Odesa's shopping mall, a warehouse and a military airfield.
"I understood it won't stop and we had to prepare everything that can help … we decided that this place, the catacomb, is the best [way] we can prepare," Mr Mauser said.
The group has chosen a particular part of the catacombs which has a suitable structure.
It consists of three connected shelters built in Soviet times that could house more than 1,000 people.
"It has three or four entrances: even if one entrance will collapse, we can exit through another."
Preparing the catacombs
Despite the natural advantages, the tunnel network is not a ready-made bomb shelter.
Stretching over 2,500 kilometres, the catacombs were created in the 19th century for limestone mining and were later used by partisans to fight against Nazis during World War II.
Parts were then prepared as a nuclear bomb shelter during the Cold War but abandoned as the Soviet Union collapsed.
"So we have really lots of jobs to do … everything is destroyed here and we have to rebuild it," Mr Mauser said.
Volunteers have prepared the catacombs by clearing debris, making electricity lines and installing LED bulbs and wooden benches with thermal insulation, he said.
Mr Mauser has a bomb shelter under his apartment, so has not needed to use the catacombs himself.
But more than 100 people, particularly residents living in newer buildings that did not have bomb shelters, had used the catacombs shelter during air raid alerts, he said.
Demand for safety beyond 'rule of two walls'
Sofiia Marchuk remains in Odesa, hoping to complete her international relations studies at the city's Mechnikov National University.
"The attacks have worsened because most of them are targeting civilians," she told the ABC.
Despite this, many people were planning to stay, as some Ukrainian refugees were now trying to return home, she said.
Ms Marchuk explained that most people used their car parks or basements as shelters.
Those who can't make it to shelters have to rely on the "rule of two walls" method to protect themselves.
This involves finding a position in the house between two walls — the first wall takes the force of the explosion, while the second works as a shield against shrapnel.
Life in Odesa was a "life-war balance", with people continuing their everyday activities, Ms Marchuk said.
She has seen people still going for a morning coffee or even doing workouts.
"People are combining their activities with volunteering and helping the army with what they can," Ms Marchuk added.
"All I can say [is that] people in Odesa are more concentrated on helping those who really struggle."
"We feel hope that it will all end soon with our victory and we will rebuild our country, and people will be able to visit Odesa and see how beautiful it is."
'We can save almost everybody'
Not all catacombs were suitable to be used as bomb shelters, Mr Mauser said.
Most only have one entrance and are disconnected from each other, and a bomb shelter needs to have two.
They are also made of different types of stone — some are strong enough to withstand explosions while others may collapse.
"If artillery shelling intensifies, I think we can build five or six big catacomb bomb shelters in Odesa," Mr Mauser said.
"Odesa's catacombs are the biggest underground system in the world, we are talking about more than 1,000 kilometres.
Unemployment and financial challenges
The plan is to make the catacombs more liveable, but the group is restricted by its lack of financial resources.
"We need electrical generators, we need more toilets … All that is built here is made by donations from people from Odesa," Mr Mauser said.
"I don't have any job now, I think 50 per cent of people in Ukraine now don't have jobs."
According to the International Labour Organization, nearly 5 million jobs have been lost in Ukraine since the war began.
Leonid Tanatarov, an Odesa psychologist and catacombs tour guide, is among those who lost their job.
"In peaceful times, one of my favourite jobs was [giving] a tour inside the catacombs," he said.
Living and adapting in war
Mr Tanatarov is looking to get another qualification not affected by war, such as IT, although it is not his area of interest.
He is now doing various volunteering work, including answerings calls on a psychological helpline and delivering humanitarian aid to those in need.
"Unclear future provokes mental instability and neurosis. People are losing earth under their feet, we help them to find stable personal ground," he said.
Mr Tanatarov said in the first weeks of war, people were "tense".
"Now it's the opposite. Many refugees are coming here [to Odesa], escaping war zones in the East," he said.
He said despite the frequent air raid alerts and looming missile strikes, the fighting was less intense than in some other parts of the country and Odesa was adapting.
"Businesses are open. Food markets, restaurants, shops, everything works. Only hotels stand empty," he said.
"Of course, there are less people, less cars. Sea trading is blocked, so the port stands still."
He has no plan to leave Odesa and is not worried about a further escalation.
"It's not a way [to live] to fear things which have not happened yet."
