The Basilica of Santa Sabina on the Aventine hill is widely regarded as the most beautiful early Christian church in Rome. It is the oldest church to have preserved its original colonnaded rectangular plan and architectural style, providing a glimpse into what churches from that time, including the original St. Peter’s Basilica, may have looked like. 

Indeed, the exterior of the church, with its large windows made of selenite, not glass, appears very similar to how it did when it was built in the 5th century. The basilica was built by Peter of Illiria, a Dalmatian priest, on the site of the house belonging to  Sabina, a Roman matron turned saint, and near an ancient temple dedicated to Juno (24 columns from the temple were used for the construction of the church).