The bone and tile floor was found in a building in Alkmaar's historic center. Municipality of Alkmaar

Archaeologists have made a surprising discovery in Alkmaar, a Dutch city famous for its cheese market. In a building under construction, they discovered a mosaiced floor made of tiles and sawn cow bones.According to a statement from the municipality of Alkmaar, it appears that the floor was originally made entirely of tiles. When the tiles were broken, the gaps were filled with cow bones. All of the bones are either metacarpals or metatarsals, which are parts of the lower legs of cows. Researchers believe the pavement may date back to the 15th century.

“We were very happy to have the opportunity to see this bone floor with our own eyes,” Nancy de Jong, an archaeologist working at the site, said in a statement, according to a translation by the NL Times. “It is always a privilege to discover something from the distant past and to contribute new information to the history of Alkmaar.”

       Archaeologists were invited to examine the floor during the building's                                                  renovation. Heritage Alkmaar

Alkmaar, located about 25 miles north of Amsterdam, is known for its traditional Dutch cheese market, the oldest in the country. The city already had a municipal cheese factory in 1365, and the first known record of its cheese market dates back to 1408, according to Kristina Killgrove of Live Science. By the 1600s, Alkmaar's market was trading millions of pounds of cheese, exporting it throughout Europe and its colonies. Alkmaar became home to the Dutch Cheese Museum in 1983.

The researchers came across the cow bone floor when they were invited to examine a house that was being renovated in Achterdam, Alkmaar's red-light district. As the archaeologists point out in a Facebook post, the house was built around 1609, but the tile and bone floor may be older: the current house could have been built on older foundations. As de Jong says in his statement, the floor was badly worn from heavy use.

Other cow bone floors have been discovered in the Holland. A strikingly similar example was discovered in the nearby town of Hoorn, and others were found in Enkhuizen and Edam. All three probably date from the 15th century.

The researchers say that tiles were a common and inexpensive material in the 15th century Holland, so they don’t know why the floor builders used cow bones. The bovine material could simply have been a quicker and slightly cheaper solution to a broken tile floor, according to the release. Alternatively, the bones could have been included because they were associated with the activities that took place in the building. The researchers are continuing to study the site to learn more about its origins.

“The discovery of this floor is incredibly interesting,” said Anjo van de Ven, Alkmaar’s heritage councilor, in a statement, quoted by NL Times. “In the historic center of Alkmaar, it is essential to treat the land with care. There are still many hidden stories waiting to be discovered.”