The location of the ancient district of Bauli has always had a central role within the archaeological research in the so-called Campi Flegrei, in the Gulf of Naples. Ancient literary sources mentioned this place in relation to the well-known phenomenon of "villa society" that characterized the Gulf of Naples, especially the Baiae-Misenum peninsula. Cicero, Pliny the Elder and Varro mentioned Bauli as the place of the orator Q. Hortensius Hortalus' maritime villa, which was particularly famous for its many fishponds. Other literary sources have contributed to reinforce the thesis, strongly defended by Amedeo Maiuri, that ancient Bauli was located at the place of modern Bacoli, where many remains of fishponds and other ancient buildings are considered to have been part of Hortensius' villa in Bauli. Few eminent scholars - such as Karl J. Beloch - contrasted this theory, proposing a different interpretation of the ancient texts that has led to locate Bauli near the Lucrino Lake, E of Baiae. The goal of this paper is to present new data from GIS spatial analysis that can contribute to evaluate both theories and to answer the question about the location of Bauli. The viewshed analysis tested Cicero's passage stating that from Hortensius' villa in Bauli it would have been possible to see his villa in Pompeii if the distance was shorter. The viewshed rasters calculated for three observation points corresponding to Maiuri's and Beloch's location of Bauli provide new important data for the solution of this topographical question. By relating spatial analysis to the information reported by the ancient sources, together with the archaeological traces, it is possible to confirm the hypothesis that Bauli was located between Baiae and Misenum, in the modern town of Bacoli.