Plaster copy of Block Ι which is exhibited in the British Museum in London. This is the narrow side of Block XLVII (Ακρ. 1145) belonging to the north frieze. Block I depicts a parade marshal (teletarch) in an almost frontal pose, turning his head towards the riders who follow in the procession. Clad in a himation that leaves part of his torso exposed, he supports his weight on his right leg, relaxing the left one. His left arm is bent and in his raised right one he would have held a staff rendered with paint on the relief’s background.

The frieze on the west side of the Parthenon shows the riders preparing to take part in the procession of the Athenian people during the Panathenaic festival, in honour of the protectress of the city, Athena. The procession's destination was the Temple of Athena Polias on the Acropolis. Its purpose was the transportation of the Panathenaic peplos destined to adorn the age-old xoanon of the goddess and the offer of a grand sacrifice of animals at the Great Altar outside of the temple.

The horsemen on the west frieze are in the Kerameikos district, where the procession started. Some converse, some others fasten their sandals, some of them bridle their horses or try to soothe them, while a few horsemen are already galloping in loose formation.

The west frieze is preserved almost intact as the bombardment of the Parthenon by the Venetians under the command of the general Francesco Morosini in 1687 did not affect this side of the temple. Its total length is 21.18 m and is composed of sixteen blocks. Fourteen of them are displayed in the Acropolis Museum after they were removed from the Parthenon in 1993 and kept in the old Acropolis Museum for fifteen years. Blocks I and II are in the British Museum in London, where they ended up after they were forcibly removed by Thomas Bruce, lord of Elgin, between 1801 and 1804, when Greece was still under Ottoman occupation.