There is an excellent website written by Susan Payne (with full references) describing what little we know of Lincoln’s Eleanor Cross HERE. My description below borrows heavily from Susan’s account:

The Lincoln Eleanor Cross

There is a piece of late 13th century carved stone, said to be a fragment of Lincoln’s Eleanor Cross, on display in the grounds of Lincoln Castle. It is thought to be a section of the skirt of one of the effigies of Eleanor from the memorial cross. It has been there since at least 1906, when it is mentioned in The Lincoln Castle Guide Book published by Mortons.

The fragment of Lincoln’s Eleanor Cross as currently displayed in Lincoln Castle grounds (Richard Croft)

Lincoln was the first resting place of Queen Eleanor and it was here that her body was prepared for the twenty-one day funeral procession down to London. Eleanor’s viscera were removed and entombed in Lincoln Cathedral. An elaborate sepulchre was constructed for them – but this was destroyed in the Civil War.

Eleanor’s tomb in Lincoln Cathedral – destroyed in the Civil War. A restored version was constructed in 1891.

It is thought that Eleanor’s body lay at St Catherine’s Priory, which is near the South Bar Gate – the southern limit of Lincoln City. Subsequently, this was the place where the Eleanor Cross was constructed. Today, we would think of the location as close to the junction/roundabout of High Street, St Catherine’s and South Park.

John Leland mentions Lincoln’s cross in his ‘Itinerary’  of 1535-1543 . . .

There lay a suburbe also without the Barre gate, by southe of the toune, and streachid toward a village caullid Brasebridg, [a litle] without Barre is a very fair [crosse] and large, and S. Catarines st[andeth in] this suburbe on the sou[thwest] side of [Barre gate.]

and a Lincoln municipal document of 1624 mentions the Eleanor Cross noting: ‘Ordered the Queen’s Cross without Barr Gates to be repaired’.

The site of the Eleanor Cross appears to be shown on John Speed’s draft of the town plan of Lincoln which he drew in 1607. This resulted in the first printed map of the City of Lincoln, but the cross is not included on the published versions of the map. On the draft plan, it appears as a tiny conical symbol with the letter ‘E’.

Detail of the South Bar Gate area, from John Speed’s draft of the Lincoln map – the Eleanor Cross is arrowed

The cross was presumably demolished during the Civil War – later maps (e.g. Marratt, 1817) show only ‘the site of the Eleanor Cross’ near this location.

In 1863, it was reported that E J Willson (1787-1854), architect, antiquary, county surveyor and mayor of Lincoln, had identified ‘a mutilated female figure which had lain as a footbridge over a neighbouring ditch’ as a fragment from the Eleanor cross. ‘Mr Burton of this city (a gentleman who has occasionally done good service to local archaeology) has now the fragment in his grounds.’

The ‘Mr Burton’ was probably Frederick Burton  (1798-1874), a Lincoln solicitor who lived at Lindum House, not far from Lincoln Cathedral. It is likely that the fragment of stone was removed to Lincoln Castle some time after Burton’s death in December 1874. In 1884 the Castle grounds were opened to visitors and would have made a suitable site for the display of this historic stone.

Over the years, the Eleanor stone at Lincoln Castle has been variously displayed and described . . . yet its authenticity as a fragment of Lincoln’s Eleanor Cross, whilst appealing, remains unconfirmed.