Archaeologists hope to find out more about what could be a 2,000-year-old warehouse over the next few weeks.
A team of 50 are taking part in the excavation of a corner of a Roman fortress in Caerleon near Newport.
The dig will open a large trench over the building, which is believed to have supplied the Roman legion.
Dr Peter Guest, of Cardiff University, said: "Store buildings are a largely unknown feature of legionary fortresses."
The experts from Cardiff and University College London will also keeping a blog updated of their progress in excavating the remains of a monumental courtyard building in the south-western corner of the fortress, which was known as Isca.
'Archaeology in action'
The building's existence was found during geophysical surveys and trial excavations last year.
It is hoped that this summer's dig will provide a wealth of new information about the storage facilities, provisioning, and supply of Roman soldiers in Britain.
Dr Guest, of Cardiff's school of history and archaeology said: "Our work is the first research excavation conducted on a military store in Britain.
"We hope that our findings will not only improve our knowledge of the fortress and its inhabitants, but also tell us more about the history of the fortress and Roman Britain.
"This is real archaeology in action and we are looking forward to an exciting summer in Caerleon."
As well as keeping in touch online, the public will invited to join twice-daily tours of the site, where they can see the latest archaeological finds.
Caerleon is one of the most important Roman sites in Britain, was one of three permanent garrisons, and was home to the second Augustan legion.
But excavations at the other sites in Chester and York are difficult, which makes the work at Caerleon unique.
By 74 AD, Caerleon had become the main administrative centre for the Roman army in Wales, and the site includes a bathhouse and an amphitheatre, which had a capacity for 6,000 spectators.
The project is supported by Cadw and the National Roman Legion Museum.
Site tours will run at 1100 and 1430 BST daily (except Saturdays) and special events are being organised for Caerleon's Roman Spectacular Military Weekend (28-29 June) and National Archaeology Week (12-20 July).