La Horca del Inca - an astronomical observatory?

While celebrating the International Year of Astronomy 2009, some government and private institutions in Bolivia pointed out the need to raise a petition to UNESCO and the IAU aimed at declaring the monument known as 'La Horca del Inca' (The Inca's Gallows) to be an astronomical World Heritage Site. The request was made because La Horca del Inca was assumed to be a pre-Columbian astronomical observatory. In this paper we analyze the reliability of that postulate through a twofold approach: 1) by examining the most relevant publications, both archaeological and astronomical, that conclude that the site was indeed a pre-Columbian astronomical observatory; and 2) by independently visiting and surveying the monument and its surrounding area.