It’s not just the art that makes a museum worth visiting, it’s the overall experience—something I was reminded of on a recent trip to the Louisiana Museum of Modern Art outside Copenhagen. Bad timing and an unpredictable Scandi summer rain had rendered the revered museum’s seaside sculpture gardens somewhat of a bust, but as I approached Dia Beacon’s earth-toned, unassuming brick facade on a splendid Hudson Valley summer afternoon, I knew I was in for a redemptive treat.  This year, the Dia Art Foundation is celebrating its 50th year, so finding the Dutchess County museum with a halo glow around…