Golestan Palace represents a unique architecture and decorative art which was common during the Qajar era mostly under Nasser al-Din Shah.
There is a mansion inside this palace called Almas or the Diamond. “Diamond Mansion” is definitely an appropriate name for this beautiful structure in Golestan Palace; a mansion that was founded during the reign of Fat’h Ali Shah, but Nasser al-Din Shah changed its appearance and decorations.
The building has been named so given its interior mirrors. Another amazing beauty of this mansion is the interior architecture of the building, including three porches of mirror work and narrow and elongated arches, which are covered on the northern side of the hall with large sash and beautiful coloured glass.
Interestingly, in the Nasserite era, most of the arches and truncated arches of this hall were turned into Roman arches, and the walls of the hall were decorated with various types of foreign wallpapers.
Here are the photos of this mansion retrieved from tehranpicture.ir: