I recently visited a great glass museum just outside Segovia, Spain called El Real Fabrica de Cristales de la Granja (The Royal Glass Factory of La Granja). "Granja" is pronounced: "grahn-ha". The museum is owned and operated by La Granja Insulator Company, which is the present day version of Esperanza, SA, and is located across the street from the museum. La Granja makes high voltage glass suspension insulators among other insulator products. The museum had a very nice insulator display, showing both historic insulators (ESAs) as well as La Granja's present day insulator products and is comparable to the Corning Glass museum, although not quite as comprehensive. I would highly recommend a visit if you are planning on being in the Madrid area, as it is only an hour north of Madrid.