Tunnelers expanding London's Underground (Tube) stations have stumbled on a cache of more than two dozen Roman-era skulls. The skulls likely date from the first century A.D. and may possibly—just possibly—be victims of the famed Queen Boudicca's troops, decapitated during her uprising against Roman rule in 61 A.D.

The intriguing find was made some 20 feet below Liverpool Street as workers bored through ancient river sediments from the long-vanished Walbrook River, once a tributary of the Thames. The skulls and pottery shards found with them may have collected in a bend of the old river, having washed down from a nearby burial ground.

The Roman skulls and pottery are just the latest in a staggering number of archaeology marvels that have been uncovered by the $23 billion (£14.8 billion) subterranean Crossrail engineering project. The project aims to create a new underground rail line beneath London. (See "London's Underground Revealed.")

The finds cut across history—everything from 9,000-year-old Mesolithic stone tools, to medieval plague pits, to a 16th-century graveyard associated with the notorious Bedlam Hospital. Containing some 3,000 graves, the graveyard was also found near Liverpool Station, in the vicinity of the Roman-era skulls.

So what are the scholars who uncovered these storied skulls saying about their find? We asked discovery team archaeologist Don Walker of the Museum of London Archaeology.

What is the association—if any—with Boudicca's rebellion?

It has been suggested that previous finds of skulls dating to this period may belong to victims of the rebellion, and beheading is certainly not unheard of in Roman Britain. This is a possibility that must be considered but cannot be satisfactorily addressed until full analysis of all material is complete. A quick look at some of the unwashed skulls revealed no evidence of injury around the time of death. But if these people were executed, we might find evidence only on the small vertebrae of the neck and perhaps the jaw. Even if this was part of a massacre, and there is no evidence that it was, it would be difficult to link it directly to the Boudicca rebellion. Of course, we will keep an open mind for now.

What can you hope to learn from the skulls about life in Roman Britain?

Funnily enough, skeletons normally tell us much more about how people lived than how they died. This is what makes them so valuable to scientists in the study of the past, being direct evidence of our predecessors' lives and experiences. In this particular case, it is unfortunate that we only have disarticulated remains, as we can tell so much more when we have the whole skeleton to study, particularly with regard to disease. However, we will be able to look at the age and sex of the skulls to see whether we have an older or younger, or mixed, group, and whether we have mostly males or females. We will also look for evidence of disease, both in the skull and the teeth. The latter can also tell us about the early lives of the individuals and perhaps their origins: Were they brought up in Roman London, or did they come from elsewhere in Britain or Europe? (See "Rome's Ruins.")

How much of a surprise was it to find Roman skulls?

It is never a surprise to find the remains of burials in London! The size of the city and its long history mean that you are never very far away from a burial ground, whether it be Roman or later. One could say that much of central London was a traditional burial site! Museum of London Archaeology and Crossrail's archaeologists have been working for a decade to predict the likely archaeological remains in the areas of the works, and how to deal with them in advance of construction. However, whilst we knew that we would encounter burials from the 16th-century Bedlam burial ground, it was not at all certain whether Roman graves would turn up. Although known from past finds in this part of London, the sheer number of skulls we have found, currently more than two dozen, has indeed surprised us.

Have these finds changed, modified, or shaded-in previously held perceptions of life in London in Roman times, or of the ancient geography of the city?

These finds are very important, as they help us to characterize the nature and use of one of London's "lost" rivers, the Walbrook. At this very early stage, we are not sure whether the finds will change or modify our perceptions of life in Roman London. What we do know is that they will help us to fill in another gap in the Roman map of the city, allowing us to fill out the information we already have. Each archaeological investigation helps us to join the dots and fill gaps in our knowledge.

How important was the River Walbrook to London in Roman and medieval times?

The Walbrook formed a useful water supply, not only for daily life, but also for industry such as tanneries on the edge of the medieval city. However, the many branches of the stream may have been as much of a hindrance as a benefit to the Romans, who expended much effort to force the watercourses within the city of Londinium into channels revetted with timber, and [who dumped] large quantities of earth to reclaim adjacent ground for building.

How and when did the River Walbrook come to be "lost"?

Most of the stream was constricted into drainage channels during the 15th and 16th centuries, and was then covered over and lost to view, consigned to drains whose successors still run into the Thames by Southwark Bridge.

Along with the Roman skulls, you have the 3,000 graves from the old Bedlam cemetery found nearby. What will you hope to learn from them?

While much work has been carried out on burial populations from the medieval period and the 19th century, much less is known about health in the 16th to 18th centuries, the period of the post-medieval burials at Liverpool Street. It will help us to understand when and how what we characterize as a medieval community changed following the dissolution, during a period of expansion and great change in London.

What has it been like as an archaeologist to get a peek beneath the streets of one of the world's great old cities?

It has been a great privilege being part of the Crossrail project, as it has given us unprecedented access to the capital's past. We are unlikely to have ever got access to excavate sites like the busy roadway at Liverpool Street, outside one of London's mainline railway terminuses. In London, history is everywhere you look, and Liverpool Street has certainly not disappointed.

How has it changed your perception of London?

It makes you realize the great impact that people in the past had on their environment, and that we are just one small part of a very long story. As well as contributing to these big questions, these excavations give us a series of snapshots of the life of Londoners over 2,000 years: a carter in Roman Britain, struggling to get his horse up the road to a bridge over the Walbrook, and losing his horse's shoes in the deep, muddy wheel-ruts; medieval ice-skaters shooting across the frozen Moorfields Marsh; someone in the 16th century with a small gold Venetian coin used as a pendant, aping the much more expensive jewelry of their betters; a family burying their young girl in the Bedlam burial ground, wearing her beaded necklace despite Christian customs; or the local craftsmen, sneaking into the same graveyard to dump the waste pieces and failed items of bone, shell, and even elephant tooth from their nearby workshops.

Subway tunnelers have uncovered archaeological artifacts everywhere from Athens to Istanbul to Mexico City. We also asked Jay Carver, lead archaeologist for the Crossrail project, to discuss such finds in London.

What other significant Roman-era finds have been unearthed by the Crossrails project?

One of the things we are always testing is assumptions about the activities in the Roman period in areas outside the core area of the Roman city. Liverpool Street is the focal point for that research into the road network, extramural burials, local industry, and management of natural resources, and we are finding a wealth of finds there to elaborate on these topics. At places like Whitechapel out along the London Colchester Road, and at Tottenham Court Road and Bond Street which are alongside the Silchester Road (now Oxford Street), evidence for burial, suburban, and roadside settlement has been absent. Finds have been limited to numerous Roman pottery shards mixed with the backfills of quarry pits mined for the valuable brick earth that was used for ceramic building materials and no doubt contributed directly to some of Londinium's buildings.

What has been most unexpected find or finds?