Complex sentence: Excavations in the twenty-first century have thrown light on the context in which the altars were found, suggesting that most of them were deposited in pits and had probably been re-used in the foundations of a late-Roman building.
Split into simpler sentences: Excavations in the twenty-first century have thrown light on the context in which the altars were found. Many of the altars are known to have been found in pits, and this is now interpreted as re-use in the foundations of a late-Roman building.