The Church of St. Lawrence Martyr was the first parish church built outside the walls of the Castle of Montecelio, today the town of Guidonia Montecelio. According to Piccolini, the original nucleus dates to the 15th century, as the two surviving frescoes and the semicircular apse on the exterior would indicate.
Restoration work was first carried out in 1524 by the parish priest Bernardino Panicola, according to an entry in an 18th century manuscript.
The town provided further funds for restoration in 1585-86 and in 1625 Mons. Angelo Picchetti financed a complete remodel as he records in his report. This included a new position for the apse and its frescoes which then also included depictions of St. Anthony of Padua and the Abbot Pietro of Subiaco.
Following a town council meeting on 16 August 1684, the church was extended and raised, while a later meeting, on 19 March 1692, decided to move the bell tower.
In 1751, new work repaired the walls and the façade, paid for by the community of Good Government. The work was carried out by Antonio Asprucci, architect to the Borghese family, and by the Master builder Pietro del Prete who was paid 174 scudi.
The style of the church is very simple and linear, with late Baroque flourishes only apparent in the limited decorative elements. The ceiling was painted in 1772 and again in 1931 during the last restoration work commissioned by Don Celestino Piccolini.
The smooth façade holds a triangular tympanum and a single central door, whose architrave features a crest of seven stars around a central half moon.
There is a rectangular window, with moulded cornicing, over the door. The tympanum has the remains of a stucco decoration with a tablet. The fascia beneath the tympanum holds an inscription that reads COMUNITAS IN HONOREM S. LAURENTII. A.D. MDCCLI RESTAURAVIT The Community restored this in 1751 in honour of St. Lawrence.
The interior holds a nave of modest dimensions. Two niches open in the walls and one in the facing wall. The ancient semi- circular apse has been walled in and reduced to the size of a large niche and has a linear, frescoed back wall.
The two surviving images from the oldest decoration, dating to the 15th century, are on the walls, just before the presbytery. At the back to the left is the door to the sacresty. The flat ceiling is painted with doves encircled with holy rays and other decorative elements.

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