The dedication is to Pope St Gelasius I (apparently).
When the parish of San Gelasio I Papa was set up in 1972, it began worshipping in what is one of the older buildings in the suburb. This was a farmhouse before development took place.
A very simple little church was provided, but was grossly inadequate and was replaced with a permanent building. However, because this is not very near the Chiesetta has been kept as an external Mass centre.
This is a very straightforward brick box with a flat roof, rendered in white with a hit of yellow and with a dado wall in random tufo blocks. There is a single doorway, and three horizontal rectangular windows in the left hand side wall which faces the piazza. Over the far left hand corner is a single bell in a small metal cage.
That is it.
Mass is celebrated on weekdays at 17:30 and Sundays at 9:00, but the church is closed in July and August.