The palace has been plagued by structural problems, including humidity. In the winter, humidity in the palace ranges from 82 percent to 98 percent, Pignatelli said. "You can almost swim in the Domus Aurea."
High humidity causes the walls to break and creates crusting. Algae and fungus are also appearing on the frescoes, she said.
Restorers work to remove some humidity — but not all.
"The frescos would suffer even more if all of a sudden the environment became completely dry again," said Angelo Bottini, the state's top official for archaeology in Rome. Bottini added that further restoration is being planned, especially on the external structures of the palace, to remove earth and tree roots.
The vaulted ceilings were once encrusted with pearls and covered with ivory — luxuries that were funded by heavy taxation that Nero levied on Rome's population, said Pignatelli. Marble and other precious materials were imported from Greece, Egypt and other parts of Asia, while inhabitants of the area were expropriated to build the 198 acres residence.
"We have to imagine this place as full of light, luxurious, with precious colorful materials and golden leaves," Pignatelli said. "Today, we only see what time and decay have given back to us."
