Celebrations have been held to mark the 250th anniversary of Boston’s Grand Sluice.
More than 60 people gathered alongside the construction, which divides the Haven and Witham rivers, on Monday to mark the milestone.
It saw a new information board being unveiled by the Lord Lieutenant of Lincolnshire, Toby Dennis.
Guests then boarded the Boston Belle for a ceremonial passage through the Grand Sluice.
They were taken down the river to view the site of the planned Boston Barrier, before returning on the tide to the Grand Sluice to disembark.
The event was championed by Boston Borough Councillor Richard Austin who said: “We celebrated the anniversary in style. The event brought together the key people concerned with river drainage and heritage.
“There were some very good discussions about ways to increase and expand Boston and its waterways’ attractiveness to visits and tourists.”
Coun Austin told guests he had been amazed to discover the huge influence the Grand Sluice has had on the development of Boston and beyond. He said it enabled 111,000 acres of fertile land to be reclaimed for food production and turned Boston into the largest town in Lincolnshire.
He praised partnership working across nine organisations for the preparations for the day.
The Lord Lieutenant also unveiled a plaque provided by the Institution of Civil Engineers.
The Grand Sluice was the Boston Barrier of its day, designed and built by the foremost engineers of the age, a spokesman for the council said.
It is possibly the earliest surviving tidal outfall sluice still in a substantially original state, and it continues to serve its original purpose, they added.