(Photo: © Royal Swedish Opera) On March 29, the Royal Swedish Opera performed Wagner’s second opera, “Die Walküre,” from the four-opera epic, “Der Ring des Nibelungen.” Mixing interiors, epochs, and styles, the evening’s production featured (surprisingly sterile) 16th to 17th century Medieval great hall interiors for the first half and 18th to 19th century French fine art lined salon-meets 18th {…}