Taking place June 9–16 at various venues throughout Downtown, the Fenway and Back Bay, the biennial Boston Early Music Festival is one of the premier showcases in North America of music pre-dating the modern classical era that began circa 1800. Its centerpiece opera, a fully staged version of Agostino Steffani’s 1691 work Orlando, should have “Game of Thrones” fans enthralled with its mix of dragons, wizards and exotic locales. Other highlights include more than a dozen concerts, a chamber opera centered around Louis XIV’s court at Versailles and a grand exhibition at the Courtyard Marriott Boston Downtown (275 Tremont St.) that showcases Early Music tradespeople from around the world offering everything from period instruments to rare books, prints and manuscripts.