Dahshur. South Pyramid (Bent Pyramid) of Snofru (Snefru).
Caption reads:
'Side of doorway of South pyramid of Dahshûr.
Shewing pivot hole on which the flapdoor turned [drawing].
This explains Strabo's saying the Gt Pyramid
was closed by a stone which could be taken out.'
There is also a diagram showing 'door open'.