In Portugal, the official curriculum of Natural Sciences (NS) in middle and high schools has highlighted the importance of a greater school-environment relationship, and calls for the need to complement activities in the classroom with the development of practical activities in the field. The development of activities of this type, taking into account the curriculum and the potentialities of the region where the schools are located, is considered an innovative and motivating strategy to be implemented in middle and high schools, in Science Education in general, and Geosciences in particular. Recognizing the importance of these activities in teaching and learning Geology, a fieldwork activity planned and applied to students of the 7th grade, in the discipline of NS, was carried out at the end of the 2017/2018 academic year, at Pombal Middle and High School. The field activity took place in the Serra of Sicó (central Portugal), in the Leiria district because this area has a great geological interest, namely diverse karst formations and geological structures. The organization of the fieldwork followed the guidelines of the Orion model and the field script that was presented made it possible to understand scientific concepts, to favour the participation of students in their learning, to promote the scientific education of school-age citizens and to stimulate awareness of the value and preservation of the geological heritage. The results of the activity evaluation indicate that the students considered their experience in this fieldwork activity very helpful, and that it helped in the acquisition of knowledge and development of skills.