Ordinarily, I’d say that given the niche subject matter of British gardening, you could skip this one—but in 2017, it revealed a macabre secret about what was really planted here: a tomb heaped with crumbling 30 lead coffins containing as many as five Archbishops. In 1977, the museum had been slotted into the abandoned church of St Mary’s, set up as an excuse to preserve it, but—garden museum irony alert—no one had thought to dig down until they had to for to even out some paving stones. Workers found a hole leading into a chamber, put a smartphone on a selfie stick, and nearly died of heart attacks when they captured a collapsing pile of blackened and rotten coffins, topped with a gilded tin Mitre hat like your nightmare’s nightmare. You can peer into the chamber, too, through a glass panel, but you’re not allowed to go into the resting place because of the risk of viscous black “coffin liquor” spraying all over you. There are other graves you can see: Captain Bligh of Bounty fame is buried in the yard. Oh, yeah, and there’s gardening stuff. There’s also an assortment of antique gardening implements and a collection of gardening-related art, too. Fun fact: The roundabout to the south, at Lambeth Bridge, is where Clark Griswold told his kids, “Big Ben! Parliament!”