The couple, both architecture graduates, moved to London three months ago to look for work and were captivated by the views over the capital they enjoyed from their 23rd floor flat.
Miss Trevisan, 27, who completed her master's degree in architecture at Venice University last year, posted numerous photographs of the urban vista on her Instagram account, including a rainbow stretched across the city on June 6, with the one-word description: "Spettacolo [spectacular]".
Just one week later their joy at their new home turned to terror.
Gottardi, also 27, called his family at 3.45am and again just after 4am.
His father Giannino told Italian newspaper Il Mattino di Padova: "In the first call Marco told us not to worry, that everything was under control, that basically we must not worry.
"He was trying to minimise what happened, probably not to unsettle us.
"But in the second call - and I can't get this out of my head - he said there was smoke, that so much smoke was rising."
The grieving father added: 'We were on the phone until the last moment ... At 4.07am he told us their apartment was flooded with smoke and that the situation had become an emergency.
"The communications broke down and from that moment on we no longer had any contact. The phone didn't pick up again."
Miss Trevisan called her parents at 3am, saying a fire had broken out and they were waiting for help.
Her father Loris said: "They wanted to go down but said they could see flames going up the stairs and the smoke was more and more intense."
Seconds later the phone line cut out and Mr Trevisan said he had made 'hundreds' of unsuccessful attempts to contact his daughter since then.
The family's lawyer Maria Cristina Sandrin said: "I've heard the recording of Gloria talking to her mother and there is no hope to find them alive.
"She said goodbye. She said, 'Thank you mother for what you have done for me'."
The lawyer said the families wanted to bring the couple's remains home to Italy, but added: "We don't know in what condition we will find the bodies, if we will find the bodies."