Surrounded by the smell of stale coffee and sweat, Taoufik Bouderbala, a trained lawyer, is leading an inquiry into abuses and crimes committed under Zine El Abidine Ben Ali.
Already, in just a matter of days, he has received thousands of complaints.
On this particular day, the crowds milled around the iron gates leading to the building, restlessly waiting their turn to apply for compensation for offences committed by Ben Ali and his henchmen.
Others simply wanted to describe what they had suffered under Ben Ali's rule.
"There is impatience and an incredible thirst for justice," said Bouderbala.
"We are going to investigate, hear out the victims, the witnesses, but also the suspects," he added.
Mehdi Benahassen had waited since 4:00 a.m for his turn.
At 54, the farmer from Mahdia region dared to hope that he finally had a chance of getting even with the old regime -- and recovering land he said a corrupt official had stolen from him.
"I have been fighting for 20 years," he said, having taken the case to court three times between 1990 and 1994.
"The tribunal didn't even look at my property deeds," he said. "Instead, they just said they had lost my file."
Twenty-four year-old student Nabil Ben Brahim came from the outskirts of Tunis to try to recover a house that his ailing father had built in 2006, investing his entire life savings.
"The house was under construction. One day, an official close to Ben Ali came by and found it pretty. And he took it."
The interim government has launched investigations into the abuses committed during Ben Ali's regime.
They are also looking into the violence the security forces inflicted on protesters during the month-long uprising, during which at least 200 were killed and more than 500 injured in clashes with police.
Ben Ali finally fled Tunisia three weeks ago, bowing to public pressure.
The revolution was triggered by the suicide of 26-year-old Mohammed Bouazizi, who set himself on fire in protest at years of humiliation by local police, who stopped him working as an unlicensed fruit vendor.
Bouazizi, like thousands of others his age, had not been able to find a regular job. He came to symbolise everything that was wrong about Tunisia under Ben Ali.
Bouderbala, who formerly headed a Tunisian human rights group, is expected to publish a report for the government setting out what legal redress people should have, what compensation should be offered.
On the building's second floor meanwhile, a clerk was recording the account of Wissem Sessi, a construction worker who injured during a protest.
He had had his leg broken in two places, he said. That meant he could not work and and had no way of putting food on the table for his wife and three children.
Nearby, files and documents were piled up on a narrow table. The clerk opened one at random, which contained the photo of a young man.
"Killed by a sniper in northern Tunis," he read. The photo showed a clean entry wound, just above his heart.
In the hallway, Oualid Guidara, 31, waited his turn to apply for compensation.
He told how a policeman had arrested and tortured on January 12 after he refused to give way to pressure on his family to pay him money.
"They gave me electric shocks and beat me with a Koran," he said.
Despite the visible signs of fatigue on the officials' faces, during breaks they engaged in lively debates over how to build the new, democratic Tunisia.
But as one of them summed up: "We need to move fast, because people are angry."