The Internet is a good opportunity to modify the teaching methods and the process of learning, and to redefine our notions of education. In this paper we present how to build a “Learning by Doing” environment using the Internet and the hypertext development. In our approach the role of the students is active inside their learning process. We refer of our experience how supervisor in a teaching project, named Web Learning Environment (WLE), where we have studied the use of the Internet and its resources to develop a new learning environment. We have involved a classroom (sixteen students, aged 16-17) of a technical institute in Italy (specialisation in Information Technologies). The project has been divided in six different phases: the knowledge of the Internet, the research in the Internet, the access to the FTP, the didactics with the Internet, the communication using the "Net”, and the creation of a cooperative hypertext dedicated to the Bonaventura Cavalieri (an Italian mathematician). In this paper we describe some educational and cognitive aspects involved in the development of a cooperative hypertext (e.g., the work organisation, the educational and social targets, the interaction between students and teacher, the modification of the role of the teacher inside the students’ learning process).