The lights will go out at Lincoln Castle next month to commemorate the 100th anniversary of the First World War.
On Monday, August 4, the historic landmark will take part in Lights Out, a UK-wide event to mark the centenary of the conflict.
People across the county are also being invited to take part in the event by turning off their lights from 10pm to 11pm, leaving on a single light or candle for reflection.
The Lincolnshire County Council HQ offices in Lincoln will also be taking part, alongside landmarks around the country such as Blackpool Illuminations, the Houses of Parliament and Tower Bridge.
The event will be complemented by a candlelit vigil held at Westminster Abbey.
Councillor Nick Worth, Executive Member for Culture and Heritage, said: “A hundred years ago, the British Foreign Secretary Sir Edward Grey famously remarked that the lamps were going out all over Europe, as Britain declared war on Germany.
“What followed was one of the darkest periods of our history, and this event is a way to remember the sacrifices of all those involved.
“People around the county can also take part by turning off their lights from 10pm to 11pm, leaving on a single light or candle for this shared moment of reflection.”