Passage: The pyramid does not have internal chambers, the chambers being located underground. These were constructed in a deep open ditch dug before the pyramid construction started and only later covered by the pyramid. The entrance to the underground chambers is located north of the pyramid from a pavement in the court in front of the pyramid face. This is different from the 4th dynasty pyramids for which the entrance to the internal chambers is located on the pyramid side itself. The entrance was hewn into the bedrock and floored and roofed with large slabs of white limestone, most of which have been removed in modern times.From the entrance a 18.5 metres (61 ft) long, southward descending passage leads to a horizontal tunnel some 8 metres (26 ft) below the pyramid base. The first few meters of this tunnel were roofed and floored with red granite. The tunnel was blocked by two large portcullis of red granite, the first one still having traces of the gypsum plaster used to seal the portcullis.Behind the granite barrier the corridor branches eastward to a T-shaped magazine chamber which probably contained Userkaf's funerary equipment. The presence of such a magazine chamber, located under the base of a pyramid, is unique of all the 5th and 6th dynasty pyramids.At the south end of corridor lies an antechamber, which is located directly under the tip of the pyramid. The antechamber is oriented on the east–west axis and leads west to the king's burial chamber. The burial chamber has the same height and width as the antechamber, but is longer. At the western end of the burial chamber Perring discovered some fragments of an empty and undercorated black basalt sarcophagus which had been originally placed in a slight depression as well as a canopic chest. The chambers are protected from the pyramid weight by a gabled ceiling made of two large Tura limestone blocks, an architecture common to all pyramids of the 5th and 6th dynasties. The chambers are lined with the same material, while the floor pavement was lost to stone robbers.

Question: the chambers were made where?
deep open ditch