Nero's Golden Palace will partly reopen to visitors Tuesday, offering rare insight into archaeologists' efforts to preserve the first-century imperial residence from decay and humidity.

The sumptuous residence rose over the ruins of a fire that destroyed much of Rome in A.D. 64 and was completed in A.D. 68, the year the unpopular Nero committed suicide amid a revolt.

After an 18-year restoration, the palace reopened in June 1999, but it has been closed since 2005, plagued by structural problems, including humidity. In the winter, humidity in the palace ranges from 82 percent to 98 percent. This high humidity causes the walls to break and creates crusting. Algae and fungus are also appearing on the frescoes.

The vaulted ceilings were once encrusted with pearls and covered with ivory - luxuries funded by taxes Nero levied on the population. Marble and precious materials were imported from Greece, Egypt and other parts of Asia, while inhabitants of the area were expropriated to build the 198-acre residence.

"We have to imagine this place as full of light, luxurious, with precious colorful materials and golden leaves," one archaeologist working on the site said.