My doubt is regarding the story of Prophet Idrees' visit to heaven taken by the Angel of Death, so when Prophet Idrees, may Allaah exalt his mention, went to heaven, he saw marble palaces for the pious Muslims, so my question is this: how did Prophet Idrees recognise it as a marble palace? Had marble been discovered by then? Prophet Idrees lived a very long time ago, during Prophet Adam's lifetime, so had marble been discovered then? Or was this marble palace simply added to this story? Please clear my doubt.

All perfect praise be to Allah, The Lord of the worlds. I testify that there is none worthy of worship except Allah and that Muhammad is His slave and Messenger.

Marble was not discovered in the modern times; rather, it was known in the ancient times. Marble is defined in Arabic lexicons as follows: "A white, loose stone," as stated by the Arabic linguist Al-Khaleel ibn Ahmad (d. 170 H). The Arabic lexicons that followed all provided a similar definition.

As for the story that you mentioned, we have searched for it but could not find it in any source book.

Allah knows best.