Sekhemkhet started his pyramid complex to the North-West of that of his predecessor, Netjerikhet, and to the East of the so-called Great Enclosure, a possible funerary complex dated to the end of the 2nd Dynasty, a couple of generations before Sekhemkhet.

Sekhemkhet is assumed to have had a short reign, which might explain why his funerary monument was left unfinished. Had it been completed, it would have been slightly larger than Netjerikhet's.

The name of Netjerikhet's brilliant architect, Imhotep, is mentioned on the North enclosure wall, thus probably confirming that this monument was designed by Imhotep as well. 

Structure

Because it was not completed, the structure of the complex of Sekhemkhet is a lot more simple than Djoser's Complex. 

There was a surrounding wall, with a palace façade motiv, a central Step Pyramid with a fairly simple substructure and to the south of it, a South Tomb.

Some remaining structures hint that the design of this complex appears to have been changed while it was being built.

Above: Map of Saqqara, highlighting the location of the unfinished pyramid of Sekhemkhet.

Clickable map of the Pyramid complex of Sekhemkhet.
Source: Lehner, Complete Pyramids, p. 94-95.