At least 10 of the frescoes that are part of the exhibit depict a series of images that include birds, dolphins, dragons and palm fronds.
The images were symbolic messages for early Christians, said the Rev. Malcolm Neyland, director of the Vatican Exhibition 2002 Foundation.
The fragments from St. Nicola are the remains of decorations found in the crypt beneath the church in 1591. The collection includes the only pieces that survived the demolition of the crypt in the mid-19th century, according to the Vatican Exhibit 2002 Foundation.