The present article describes activities undertaken in the virtual world called "Euroland" to promote collaborative knowledge building, using a variety of communication formats. The communication formats available in Euroland are text-based via a chat (synchronous) and a discussion forum (asynchronous); and visual in the form of virtual objects, pictures, and photos. Euroland has been designed, implemented, and evaluated by a Dutch-Italian community composed of students, teachers, and researchers performing educational, cross-cultural, and interdisciplinary tasks. The relevant theoretical perspectives concerning collaborative knowledge building, visualization within a three-dimensional environment, and the community of learners and the community of practices models are also reviewed. A qualitative evaluation of the activities performed in Euroland is then undertaken. It is concluded that the activities involving different communication formats within a virtual world are only appreciated and used when the community of users reaches a particular level of awareness with regard to the technical and cognitive functions of each format. When integrated, the communication formats are found to have a reciprocal influence on each other. The community is able to generate new activities not planned in advance, depending upon the specific situation, which gets defined during the interaction between the various participants in Euroland. (C) 2001 Elsevier Science Ltd. All rights reserved.