The Cathedral Basilica of Saints Peter and Paul, head church of the Roman Catholic Archdiocese of Philadelphia, stands on 18th Street on the east side of Logan Square, at the Benjamin Franklin Parkway.

[3] The largest Catholic church in Pennsylvania, the cathedral was listed on the U.S. National Register of Historic Places in 1971.

[citation needed] In 2017, the shrine of Saint Katharine Drexel was relocated to the cathedral after its former home, St. Elizabeth's Convent, was closed and sold off by the Sisters of the Blessed Sacrament.

[6] With its grand façade, vaulted dome, ornate main altar, eight side chapels and main sanctuary that comfortably holds 2,000 worshippers, the Cathedral Basilica of Saints Peter and Paul is the largest brownstone structure and one of the most architecturally notable structures in the city of Philadelphia.

The cathedral, presented in a Roman-Corinthian style of architecture, is modeled after the Lombard Church of St. Charles (San Carlo al Corso)[7] in Rome.

Its Palladian façade and aqua oxidized-copper dome are in the Italian Renaissance manner, as is the spacious interior, which features an oversized apse of stained glass and red antique marble in proportions reminiscent of Roman churches.

Other notable buildings he designed include the Philadelphia Academy of Music on South Broad Street.

Constantino Brumidi painted the ceiling mural in the dome, The Assumption of the Virgin into Heaven in 1868, and the round portraits of St. Matthew, St. Mark, St. Luke, and St. John on its pendentives.