In a vast hall, scores of BAE Systems workers are busy constructing parts of the giant new aircraft carrier HMS Queen Elizabeth. It's an impressive operation using cutting edge technology.
But today's shipbuilding scene can't compare with the incredible hive of activity that was Portsmouth dockyard a century ago.
Back in 1905, the most advanced warship in the world, HMS Dreadnought, was being completed in record time. She was so big that the docks had to be enlarged and adapted to cope with this new class of battleship.
From then on right up to the First World War nine years later, a battleship was launched every year in the contest for naval supremacy with Germany. During the war, the dockyard workforce grew to 23,000 and five large submarines were built and 1,200 vessels refitted.
By the height of the Second World War, 25,000 people were employed there, doing jobs ranging from building minesweepers to preparing assault craft for D-Day.
Local historian John Sadden uses these figures to illustrate how important the dockyard became, both as the heart of the city and in creating our national naval strength.
He says: 'At outmuster time thousands of people would come out of the dockyard on bicycles. It was like the Charge of the Light Brigade. The image is very much part of our heritage and an enduring memory for local people.'
In his book Portsmouth: In Defence of the Realm he looks at how 'Pompey' grew from an adjunct to the ancient military centre at Portchester into the world's premier naval base.
He says: 'In the arms race leading up to the First World War, Portsmouth was THE major shipbuilding port. In times of war and international tension, employment in the dockyard has grown. But the downside is that in peacetime a lot of jobs have been shed.'
Portsmouth born-and-bred, John is fascinated by how Portsmouth and Gosport have been shaped by their long military history. His labour of love in writing the book has involved bringing together for the first time the history of the harbour's forti?cations and those of the city's military garrison, dockyard and naval and air defence establishments.
John's painstaking research means it is easy to look up a particular building and see when and why it was built.
Illustrated with engravings and rare photographs, many never previously published, the book provides the historical context to what we see all around us today on both sides of the harbour.
John has long had an interest in local, naval and military history. So he seemed the ideal man to write a volume he hopes will appeal to residents, visitors and historians alike.
The 52-year-old from Portsea says: 'It took me about a year to write and involved a lot of research, from Portsmouth Central Library to the Royal Navy Museum and the Imperial War Museum. Having grown up in this area, local history is of great interest to me. I found out a lot I didn't know and the detail helps to build up a fuller picture.'
Every time he goes to work, he is reminded of military history. John's an archivist at Portsmouth Grammar School and his office is in what used to be officers' accommodation at Cambridge Barracks, used by the army until the 1920s.
He explains: 'Portsmouth's whole development ran parallel with the expansion of the navy. The city wouldn't be the same without that and its development as a garrison town. It is hard to over-estimate the impact that has had on the character of the city and also of Gosport, where support services for the navy were provided at places such as Priddy's Hard and the Royal Clarence Victualling Yard.'