Inside the North or Red pyramid
The North Pyramid's substructure is a continuation of the developments seen at Meidum and the Bent Pyramid. From high up in the pyramid a long corridor descends to ground level. At this point are two almost identical tall antechambers with corbelled roofs of great finesse, technically far in advance of those at Meidum. A short horizontal passage leads from the second antechamber, high up to deter robbers, to a corbelled chamber, 15 m (50 ft) tall, built within the masonry of the pyramid. Fragments of human remains were found in the burial chamber, but it has not been ascertained whether or not they are from the royal mummy.
 

Source: The Complete Pyramids; Mark Lehner; Thames and Hudson; 2000 (possibly the best all-round book available on Pyramid). Dashur Pyramid Complex.