The exhibit’s centerpiece, however, was a gargantuan slab of Titanic’s hull, known as the “big piece,” that weighs 15 tons and was, after several mishaps, hoisted by crane from the seabed in 1998. Studded with rivets, ribbed with steel, this monstrosity of black metal reminded me of a T. rex at a natural history museum: impossibly huge, pinned and braced at great expense—an extinct species hauled back from a lost world.