The Conquest of Peten Itzá in Guatemala took place on March 13, 1697, headed by Martín de Urzúa, governor of Yucatán at the time. However, prior to the same, several entries were verified to evangelize the region headed by Franciscan friars who, from the province of San José de Yucatán, raided to bring the Catholic faith and the European ways to the population who lived in the lands of Peten and that they were free from Spanish rule. In fact, such entries had, in principle, entirely religious purposes; however, the pacification of the region was also sought as it was a space of exclusion where entire communities composed of the so-called “montaraces” -mayas who had escaped from the haciendas and the tribute - remained free and in constant contact with Mayan groups that had not been conquered, like the Itza, who ruled from the city of Tayasal in the heart of Lake Peten Itza. That territory, a huge wild border between Yucatán and Tayasal was called "the mountain". In order to understand the interesting symbolic exchange in that border, I study the entries made during the seventeenth century by those friars, their chronicles and contrast them with the speeches of their counterpart, the Itza; also, several documents from the General Archives of the Indias regarding the Peten region. To do so, I will explore the contributions of Yuri Lotman in its systemic approach based on the semiosphere and its concepts of border and periphery. By understanding the symbolic and discursive exchange between such dissimilar worlds (the western / regular Christian of the Franciscans and the Mesoamerican / colonial of the Itza and other ethnic groups) there will be evidence of encounters and disagreements that will later be integrated into the current discourses of the Itza and mestizos of the region. Of course, just like Lotman states, “The border of semiotic space is the most important functional and structural position, giving substance to its semiotic mechanism. The border is a bilingual mechanism, translating external communications into the internal language of the semiosphere and vice versa. Thus, only with the help of the boundary is the semiosphere able to establish contact with non-semiotic and extra-semiotic spaces”. Here, at the so called “mountain”, numerous exchanges were made in times of “peace” and some others after the conquest of the region. But it also brought confusion and misinterpretation wich leaded to conflict and difficult the negotiation between mayans and spaniards. So, from the conception of religion to the logics of govern, mistakes were made, and contributed to, in terms of Lotman, a change in explosive mode: the armed conquest of Peten in 1697.