In which valley was Achan stoned and buried under a pile of rocks?

Answer: Achor

Achan and all he had were brought to the Valley of Achor, where Israel stoned him and heaped a large pile of rocks over him.

“Then Joshua, together with all Israel, took Achan son of Zerah, the silver, the cloak, the bar of gold, his sons and daughters, his oxen and donkeys and sheep, his tent, and everything else he owned, and brought them to the Valley of Achor.”— Joshua 7:24 (BSB)