Referred to as La Hacienda by the townsfolk, the small, excavated tombs that are the Xaaga ruins lie about 4 kilometers (2.5 miles) southeast of Mitla, the tombs at the center of a two-hundred-plus-year-old crumbling Spanish hacienda, hence the name, the grounds now overrun with weeds, the hacienda’s roofs having collapsed long ago, its adobe walls left to crumble. And so, except for a small piece of Mesoamerican history and the degeneration of time since the late colonial era, there's really not much to see here. Still, Xaaga makes for an interesting side strip after visiting Mitla.
From the city of Oaxaca, only take Mitla-bound colectivos (Mex$20) originating from the sitio southeast of the Abastos market or Mitla-bound buses departing (Mex$14) from the main second-class bus station north of the Abastos market heading to Mitla. These same colectivos and second-class buses can be flagged down at the northeast corner of the baseball stadium (De Los Derechos Humanos and Eduardo Vasconcelos). Get off at the bus stop located at the intersection of the main road into town and Morelos, which goes off in a 45 degreee angle. The Mitla ruins are about a kilometer straight down Morelos, which turns into 5 de Febrero after Independencia.
The colectivo sitio for Xaaga is about half a kilomter, quarter mile, past the bus stop on the main road, at the intersection of Cempoaltepetl and Independencia. Mototaxis run along Cempoaltepetl if you don't want to walk it. Colectivos to Xaaga are Mex$5.
To visit the ruins, you'll have to find the caretaker of La Hacienda to let you in, since the gates to the Hacienda and tombs are always locked. The colectivo driver will probably help you find the caretaker. Be sure to tip him or her for the extra effort. Otherwise, just ask anyone in town, they should know where to find the caretaker. The caretaker generally acts as tour guide and will answer all your questions. Be sure to tip him as well.
The sitio for colectivos back to Mitla is in front of the church. Ask the caretaker to show you where it is.