The Ayutthaya City Pillar, or Lak Muang shrine, is located across the roundabout from Wat Phra Ram. It houses a stone pillar that once marked the provincial center of Ayutthaya. The pillar resembles a lingam, which is a phallic symbol associated with Brahmins.
This shrine and the pillar within it is a modern construction erected in the twentieth century.
The significance of the city pillar changed substantially during the Bangkok era, and it wasn’t until the 1990’s that provinces were actually directed to erect city pillars in their capital cities.