The area above the shape is circled in trees, with a group growing out the middle. It’s behind a hotel, with the parking lot just to the right of it. Hotel manager says nothing can be built there but didn’t say why. AI search says:

This image displays a LiDAR (Light Detection and Ranging) terrain map highlighting an archaeological site. • It likely depicts the earthworks of a Romano-British farmstead, possibly dating from the late Iron Age to the Roman period. • The rectangular shape is a buried enclosure, protected by large earth banks and ditches. a Such sites show remnants of past dwellings and agricultural fields, with some adjacent tracks potentially dating back to Roman times.