my landscape has a bright aquare what cab i do?

there it’s a bright square on my landscape.if i close the lights it stays there,if i close everything except the landscape it stays there and you can see it with or without texture s

o what can i do?

Looks like old lighting data, have you tried rebuilding lighting? (As suggested by the red warning text in the top left).

To only build lighting, click the dropdown arrow to the right of the Build button and chose “Build Litghting Only”