"Significant" archaeological finds from the Roman town of Verulamium have been uncovered during gas main works in St Albans.
Verulamium was the third largest city in Roman Britain and has been mapped by various excavations over the years.
The new holes revealed the location of the corner of the town wall and a previously unknown house.
District archaeologist Simon West said: "It's like having a jigsaw... and now there are two more pieces."
He added: "Eventually [we will] see the whole picture and now we have new information that we can tie down rather than speculate."
Verulamium was sited to the south west of what is now the city of St Albans in Hertfordshire.
Much of it was used for the construction of medieval St Albans and the Abbey and the rest is largely unexcavated and covered by park land.
Mr West said: "It's significant in that we've found the very corner of the town wall as it bends round [from the gate house to the Roman wall above the lake].
"We knew it must be there but we'd never seen it and never known precisely where it was.
"Plus we've found no evidence that there was a corner tower which gives us more information."
Another dig unearthed evidence for the interior of a house in an area previously thought to have been the location for a road.
The remains of an Opus Signinum floor - made of tiles broken up into very small pieces - have been uncovered.
"In theory this should have been a cross roads and what we've got are the remains of a Roman town house," Mr West said.
"There are individual pieces of Roman mosaic which suggests it was probably quite a high status house.
"We've now got to move the Roman road on [our] map to fit in the building."
The findings will now be recorded and the holes filled in, but finds such as pottery and animal bones will go to the Verulamium Museum.
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