Extensive results are presented for acoustic and meteorological measurements at the ancient open theatre of Epidaurus. The analysis of the results, illustrates most aspects of the theatre's acoustic properties, indicating the pattern and mechanism for the early reflections, the spectral response of the theatre, aspects of time-frequency response interaction and aspects of the spatial impression. The results also verify predictions of earlier acoustic models for this theatre and indicate no significant effects from environmental factors such as temperature, humidity and wind variations across the theatre. Measurements with the theatre partially full with audience show no change with respect to speech intelligibility. The results restate the renowned exceptional acoustic characteristics of the theatre for speech, for all listener positions.