Archaeologists from the Palace Museum have unearthed four square underground foundations made from bricks in the early Ming Dynasty. The foundations were used to support columns.

Wu Wei, an archaeologist working at the site, said the 1.6-m-high foundations are about 4.4 m wide, making them the biggest brick-made column footings found in archaeological excavations in China. The foundations are known as sangdun in traditional Chinese architecture.

"If a foundation is so huge, just imagine how grand and tall the column above would be," Wu said at the site late last month. "They may unveil a palatial construction from the early Ming Dynasty that was much bigger than the existing ones in the Forbidden City."

Taihe Dian (the Hall of Supreme Harmony) in the core of the Forbidden City, which was used exclusively for the most important royal rituals, is the largest and highest construction in the royal compound. Nevertheless, its column cornerstones are only 1.6 m wide.

"We cannot see their underground footings, but we estimate that they could be about 2 meters wide, based on our previous experience of studying other Ming constructions. This is much lower than our new archaeological findings," Wu said.