Tenants Stefano and Gino, both 24, said they were throwing a birthday party and invited about 20 people, thinkSPAIN reported.
"They all brought other mates along and we couldn't leave them out in the street," Stefano said. "The doorbell never stopped ringing and I was constantly busy serving drinks to everyone."
Police were called to the building at about 2 a.m. by neighbors complaining about the noise.
"We were terrified the ceiling would collapse with the weight of all the people inside," said Amparo M., who lives below Stefano and Gino. "The police counted 135. I couldn't believe it."
Police were unable to enter the apartment because of the number of people in it and ultimately kicked everyone out.
"They told me off because we were disturbing the neighbors," Stefano said of the police.
Sefano said police filled out a report and that he will likely face charges for noise nuisance, adding that his friends offered to help pay any fines.
"We've already spoken about it and everyone would chip in a bit of money, but I hope there'll be no need. We did what we were told when the police came," he said.
"We're young, it's normal that we would hold parties," Stefano said. "The other night we went over the top, but it won't happen again."