If Persepolis is the jewel in the crown of Iran, then the same must be true for the stairs of the Eastern Portico of the Apadana Palace in Persepolis.
Originally all of the bas reliefs together with most of Persepolis itself were brightly coloured.

The Eastern Portico is divided into three parts: The northern staircase with representations of Achaemenid dignitaries, The Staircase Centrepiece, and
the famous southern staircase, showing representatives of all the subject nations with a procession of people bringing tribute to Darius the Achaemenid king.

There is also some disagreement about whether all of the delegates have been identified correctly.
I have used the delegate identities provided on site, but I have also specified the alternatives in brackets (more info).

The oblique (slanting) tier (left to right): Ethiopians (Maka/Nubians), Libyans, Zarangians (Carians), Arabs from Jordan and Palestine and European Scythians (Thracians).
The Top tier delegates (left to right): Sagartians, Bactrians, Egyptians (?)- badly damaged, Arachosians (Arians), Arians from Herat (Parthians) and Medes.
The delegates on the middle tier (left to right): Amyrgian Scythians (Sogdians), Gandharians, Pointed hat Scythians, Assyrians, Babylonians, Armenians.
The delegates on the bottom tier (left to right): Indians from Sindh, Parthians (Arachosians), Ionians, Cappadocians and Lydians.

Unfortunately the protective roof over the staircase means that the tonal range is limited when trying to photograph the bas reliefs.
(The bas reliefs in the adjacent Tripylon Staircase do not suffer the same fate and are wonderfully illuminated in the setting sun).

You can also compare the delegates represented here with those shown on the tomb of Darius the Great at Naqsh-e Rustam.

I have enhanced the photographs of each delegation in order to reveal their otherwise hidden beauty (4 months of work). I hope you find them as fascinating as I do.