Chiesacchia is a ruined mediaeval church in a field opposite the Pizzeria Arcobaleno, Via Laurentina 996 in the suburban zone of Vallerano.
There seems to be very little notice taken of this ruin, apart from an info.roma page here.
The edifice is within the ghost of a rectangular enclosure, itself in a large field containing a (now disused) farmhouse. It is in brick, on a rectangular plan comprising a single nave of seven bays with a large semi-circular apse slightly narrower than the nave. Each bay had a single vertical rectangular window in each side, fairly high up.
The ruin has lost all the lintels of the windows and the fabric above them. Further, the façade has vanished except for a narrow fragment on the left hand side, and the right hand side wall has also gone for the first two bays. The façade fragment has what is either a buttress, or the remains of a side wall of an entrance loggia.
The field seems to be zoned for possible future development. It is fenced off and inaccessible. The interior of the church is full of scrub..
On the hill to the south-east is a ruined mediaeval tower, the Tor Chiesacchia.