The foundations of the ancient Rattanakosin City Wall, built in the reign of King Rama I  along the Chao Phraya River, was discovered underneath the 60th Anniversary Building at the Thammasat University (fig.), during restoration works in 1997.

The city wall was built in multiple thick layers of large bricks in good condition, each leveled off and then topped with scrap bricks mixed with clay. On the lower sides were ca. 1.5 meter long pieces of wood, that were angled at 15 degrees vertically, used as supports for the foundation of the wall.