The floor plan for the Bayreuth Opera House. From: 
<ul><li>Burlingame, Edward L., <i>Art, Life, and Theories of Richard Wagner</i>, New York, Henry Holt and Company, 1875  <a rel="nofollow" class="external text" href="http://historical.library.cornell.edu/cgi-bin/cul.cdl/docviewer?did=cdl137&amp;view=50&amp;frames=0&amp;seq=9">Available Online</a>  Copyright expired.</li></ul>
Unknown author<span style="display: none;">Unknown author</span>
see above