Between 1244 and 1276, Abbot Henry renovated Sacro Speco, fully changing its aspect. The inside was wholly changed by introducing the "ad quadratum" Bernardine plan, which the Cirstercians spread all around Europe and which is present in Latium at Fossanova and Casamari. Of the same period is the building of the wide plan of the lower church, a wide rectangular space divided into three rooms covered with cross vaults: one room is rectangular, the other two are square.
Today, the entrance of the lower church is from the transept through a stairway, which presents on the right wall a Byzantine fresco, which represents the text of the bull, by which, on 4 July 1202, Pope Innocent III gave special favours to the Benedictines of Sacro Speco. Then, above the text of the bull, Conxolus frescoed another Innocent III, wearing a red cope, the Pallium, and on his head the tiara with just one crown. Very few is known about this artist, perhaps he was Roman; the most of the frescoes of the lower church are attributed to him and to his assistants.
The first span is situated near the Holy Step, on the left of the church. On the sides of the window we have, in two frescoes, Florentius' attempt to poison the Saint. On the left we a woman dressed in red who offers St. Benedict, sitting in a cave, some poisonous bread wrapped in a large white cloth. In the painting on the right, St. Benedict orders a raven to take away the poisonous gift. Higher up, above the door of the Choir, is the Miracle of St. Placid; the young Placid had fallen into Nero's lake and was saved by St. Maurus who, in obedience to St. Benedict's order, runs on the water of the lake without being aware of it. Lower down is the Miracle of the Goth. The lake is represented very simply by a large white rectangular surface with wavy edges. On the left is the Goth who hands St. Benedict the handle without the hook which has fallen into the lake; on the right is St. Benedict who dips in the water the handle which is miraculously rejoined to the hook. The scene is represented with much feeling and expression
The second span is situated on a lower level than the first one, because it follows the sloping down of the rock. On the left, near the entrance to the Sacro Speco, there is a fresco of Blessing Christ among Angels. On the wall on the left of the stairway that leads to the second landing is a fresco in a bad state of repair, representing St. Benedict's death. On the same wall there are the frescoes of St. Stephan, St. Thomas and St. Nicolas. On the vault there are frescoes of popes, bishops and saint monks such as St. Benedict, St. Gregory, St. Sylvester, St. Lawrence and other Benedictine saints
On the left of the stairway to the upper church is a Byzantine painting of the beginning of the XIIIth century depicting Innocent III (Pope in 1216) with the white tiara. The Pope is holding the bull with which he presented some revenue to Sacro Speco in1203. On the left of the bull is St. Benedict seated with Abbot Romanus ( consecrated in 1216) kneeling at his feet. Until a few years ago, this part of the fresco was covered by another painting ( now kept in the Sacristy) of St. Benedict depicted by Conxolus, together with the other painting, which is above the same bull, Innocent III wearing a red cope, the Pallium, and on his head the tiara with just one crown. In the small apse on the left is found the name of Conxolus near a very fine fresco of Our Lady with
The Child between two Angels: "Magister Conxolus pinxit hoc opus". Conxolus, who did nearly all the paintings in the Lower Church, is a painter of the second half of the of the XIIIth century and belongs to that popular Roman School which was to have its greatest representative in Pietro Cavallini. "In the simple paintings of Conxolus is that freshness of art which begins by leaving the darkness and approaches the light by looking at life and taking it directly as a model".
On the left wall, near the fresco of the Virgin, Conxolus painted the first events of St. Benedict's Life: the Miracle in Affile of the sieve broken by his nurse and repaired by The Sign of the Cross, the Meeting with St. Romanus, by whom he is clothed in the monastic habit, and His withdrawal into the cave. " The scene are represented with a sweet simplicity. In St: Benedict's dress and gesture one sees all the joyfulness of youth."