ייִדישער מחשבֿה אויף תהילים 120:1

Tractate Middos states⁵Middos 2:5. that the Second Beis HaMikdash had “fifteen steps leading from [the Women’s Courtyard] to the Courtyard of the Israelites, corresponding to the fifteen “Songs of Ascent” in Tehillim. The Levites would stand on these steps and sing songs. [The steps] were not rectangular, but semi-circular instead.”