Bourne Castle was in the market town of Bourne in southern Lincolnshire (grid reference TF095199).
A Norman castle was built by Baldwin FitzGilbert (son of Gilbert Fitz Richard, of the De Clare family). In medieval times there was motte and double bailey castle which formed an unusual concentric plan. The castle was destroyed after being used by Cromwell's troops in 1645 and a farmhouse was built on the site. Traces of the enclosed mound and inner and outer moats are all that now survive.
The land is now a park, known as the Well Head, owned by the Bourne United Charities and is open to the public.
References
Bourne Castle Wikipedia(Text) CC BY-SA