From 1854-56, Richard Upjohn designed a new church using the old foundation and brick walls. This church still stands today. Upjohn is most famous as an architect of Gothic Revival churches (such as Trinity Church in New York City), and Gothic style was growing more popular in Baltimore at the time. Old St. Pauls, however, does not look even remotely Gothic. Rather, Updike seems to have based St. Paul's on early Christian basilicas such as San Paolo fuori la mura (St. Paul's Outside the Walls), built in Italy in 384. Architectural historian Laurie Ossman has pointed out the striking parallels between St. Paul's in Baltimore and San Paolo in Rome. First, both churches have burned down and been rebuilt--San Paolo caught fire in 1823 and required extensive reconstruction. Second, San Paolo is one of the oldest surviving (if heavily restored) Christian basilicas, while St. Paul's is the oldest parish in Baltimore. Finally, San Paolo is the oldest basilica dedicated to St. Paul, upon whose burial site it stands. The two churches thus share a namesake. Upjohn is known to have traveled in Italy and was likely familiar with San Paolo.
Inside Old St. Paul's, visitors can see the altar window, designed by Maitland Armstrong and installed in 1902. Underneath this window is a stone screen (reredos) with peacocks symbolizing the Resurrection. The church also contains several windows designed by Tiffany Studios, portraying figures such as St. Anne, St. Augustine, and St. Luke.