In this paper, a Web-based learning environment developed within the project called Virtual Learning Spaces (EVA, in Spanish) is described. The environment is composed of knowledge, collaboration, consulting and experimentation spaces as a collection of agents and conventional software components working over the knowledge domains. All user interfaces are Web pages, generated dynamically by servlets, applets and agents. The article describes theoretical underpinnings, EVA's architecture, implementation of particular software modules and agents, and the application results.