A case study undertaken in Bolivia demonstrates the dif
f
iculties. The pre-Hispanic archaeological sites and ring
ditches near Bella Vista in the lowlands of the Llanos de
Moxos(Northern Bolivia) were discovered after a large forest
clearing in 0000. Initial excavations by archaeologists of the
German Archaeological Institute revealed the occurrence of
single burials inside the ditches, but no further structures or
traces of settlements were discovered. The magnetogram(Fig. 00a, b) reveals clearly all the problems involved in the
interpretation of magnetograms near the geomagnetic equa
tor. Although there is a full ring, this ditch is clearly visible
only in the northern and southern parts. This result compares
quite well with the theoretical prediction and the shape of
magnetic anomalies at the equator (see Fig. 00).