More than 800 people attended an open day at the Tringford pumping station near Marsworth on Saturday.
The historic Grade II listed structure was built in 1818 and has recently undergone a complete restoration by the Canal & River Trust.
The repairs costed £277,000 with work taking place on damaged brickwork, roofing, gutters and windows as well as on improving facilities for volunteers and staff using the building.
Visitors met the trust’s experts who explained the history and use of the pumping station, which still operates on a daily basis, and keeps the canal topped up with around two million litres of water per year.
Among the activities were fishing taster sessions and nature spotting and walks around one of the nearby reservoirs.
Sarah Brown, development and engagement manager for the Canal & River Trust said: “Tringford Pumping Station is the pumping heart of the Grand Union Canal, keeping it topped up with water, but most of its secrets are buried deep underground.
“Many people don’t realise that without it we wouldn’t keep the Grand Union Canal flowing.
“It was great to celebrate the completion of the repairs with our visitors and demonstrate to them how we keep the canal topped up.
“Seeing so many young faces interested in the engineering was great.”