These Hitching Rings are located in the Porta dei Pispini that is one of the doors of the ancient wall of the city of Siena. There are several on each side of the gates.
About the Porta dei Pispini we can read at the stay.com (
visit link) website:
"Porta dei Pispini is one of the oldest city gates of the city. Along with Porta Romana, very similar in structure, Porta dei Pispini is part of the last walls of the city of Siena, built in 1326, and based on a design attributed to Minuccio Rinaldo.
Porta dei Pispini was originally called Porta San Viene. The internal façade was adorned with the great fresco of the Nativity painted by Sodoma in 1530-1531, remains of which can now be admired inside the Basilica of San Francesco."