Surprise bricks

Hi all, last week decided on a plan to remove the old patio in pic one and grass the area in order to relocate the patio to a sunnier spot.

After digging up all the slabs I have found what looks to be a layer of bricks underneath.

Has anyone else ever encountered this?

Original plan was to grass the area but now unsure what to do.

Thanks in advance and please be gentle this is my first time owning a garden 😆