Pärt's Spiegel im Spiegel.)
This 2005 recording for four pianos (the most common arrangement; there's also various combinations of pianos, organs, marimbas, harps and synthesizers available) is certainly a good starting point due to its duration - only, yes, only, two and half hours long (although there's even single-CD reductions available) when some recordings can top three or four hours, and live performances can far outstrip that.
So why the variety in length? Ten Holt wrote the piece in 106 small sections, and intended the players to have as much freedom as they liked to play around with each one before a 'lead player' would indicate an advance to the next. Most importantly, of course, is how this sounds when you sit down (or indeed, walk, jog, or drive, all of which would also work well) and listen to it. Philip Glass aficionados will already be familiar with the feeling of when subtly-changing repetitive structures work their hypnotic magic over an extended period, so Canto Ostinato will be right up your street. Even more than Glass, though, I'd argue that this piece is just so thoroughly accessible and enjoyable that it's likely to become an indispensable part of the musical life of anyone who gives it a go.