Well, that's one theory put forward by archaeologists about the grand complex of palaces at Mitla. There's some evidence to support this theory - it is known that this was the burial place of Zapotec kings and heroes (Mexicans knew this place as Mictlan meaning "Inframundo" - the Place of the Dead)and the evidence of burials found here points to people who had lived into old age (a rare thing in pre-Hispanic Mexico), had a good diet and were well cared for - all indications of an elite group.
Much of Mitla now lies under the colonial town that came into being after the conquest but enough remains to show how grand and unique this place was. Two groups of buildings appear to be ceremonial centres, there is evidence that they were used ritualistic purposes, perhaps priestly initiations. Others seem to be palaces. There are no great pyramids or temples here - the buildings are of much more human scale, with long rooms and wide patios. There is some very fine decoration, a lot of it unique to Mitla - another indication of royal occupancy. Most notable are the extraordinary bands of tesselated stonework. They're all intricately geometric, some with a mirror image on an opposing wall - so meticulously laid that if the walls were to pushed together those two mirror images would lock together perfectly. Other notable features include a surprising amount of original colour and fresco on the walls. The reconstruction of one of the chambers demonstrates how earthquake damage was controlled by floating the huge stone-slab ceilings on tiny round stones on the top of the supporting walls - this allowed sufficient movement in the building to prevent it cracking apart as a more rigid structure would have done - most ingenious.
The Church Of San Pablo was built right over one of the palaces, using stone from the temples. This was standard practice throughout all Mexico until 1850 as the Spanish clergy sought to impose Catholic beliefs on the local population.
The ruins are the main reason people come to the village of San Pablo de Villa de Mitla.
If you come on an organized tour , you probably won't have a lot of time to look around more than the section of the ruins adjacent to the church and a browse through the little market area anyhow, but should you have time, the church with its distinctive domes is certainly worth a look, and those with time to call their own can make their way to the areas of the ruins known as the "Arroyo" - or Stream and "Adobe" groups that lie across the river.
It is known that the church was built directly over a courtyard and some of the tombs using stone from the demolished palaces - this was the standard practice of the Catholic church as it sought to replace the old beliefs. There's a fine collection of "santos" - carved and painted representations of Christ, the Virgin and various saints, some of them several hundred years old - in the church.
As you approach the ruins you'll find the usual collection of souvenir and handcraft shops and stalls. Much of the handcraft is locally made, some of it to distinctive Mitla designs.
The museum probably isn't worth bothering with unless you're a real fan of old pots and the minutae of archaeological digs.
After Monte Alban, Mitla is the most important archaeological site in Oaxaca. The ruins are quite unlike others to be found anywhere in Mexico - they wouldn't look out of place on the shores of the Mediterranean - they reminded me of Knossos in Crete. It seems far less haunted to me than many of the other pre-Hispanic ruins of Mexico, well worth the trip out from Oaxaca, with or without a guide.
Some 45 kms south-east of Oaxaca are the Mixtec ruins and, apparently, the best pre-Hispanic stone mosaics in the whole of Mexico.
The main grouping is the Grupo de las Columnas, centred around the landmark red domes of the Iglesia de San Pablo (built on top of the foundations of extensive buildings by the conquering Spanish in the 16th century). There are (less interesting) ruins dotted round the modern and somewhat dusty modern Zatopec town of Mitla. Most people restrict themselves to the Columnas - and it's an interesting if somewhat small site - indicated by the extensive tourist market that has developed between the ruins and the church. Probably wouldn't keep you occupied for more than a couple of hours, but could combine with a trip to Hierve el Agua (30 kms futher east).
To get there, take bus from Gate 9 of the 2nd class bus station: join an organised tour of the Valles Centrales: if there are enough of you, share a taxi and combine Mitla with Hierve el Agua