The caves gave up their secrets slowly. In 1880 a German explorer, M. F. Will, mapped the first two chambers — the White Cave and the Black Cave — and for a while it was assumed that was all there was. Then, in 1896, the owners invited Édouard-Alfred Martel, a French scientist regarded as the founding father of speleology, to push deeper. Martel found two more great caves the earlier survey had missed and, at the bottom of the system, the vast still lake that now carries his name. All told, the four caves reach some 2.4 kilometres in length and descend to a depth of about 25 metres below the surface, a labyrinth of galleries hung with stone. Martel's visit sealed the caves' fame, and the lake at their floor became the crown of the whole system.

Lake Martel is the heart of the place. Roughly 115 metres long and 30 wide, and ranging from about four metres to a dozen metres, its water lies so motionless and so clear that the boundary between stone and reflection dissolves. Stalactites hang down toward their own mirror images until you can no longer tell which way is up. The air holds cool and steady the year round, and every footstep and whisper carries far in the enclosed silence. Coloured light picks out mineral draperies overhead, formations built up drop by patient drop across spans of time the human mind struggles to hold. To stand at the water's edge here is to feel the weight of the whole island pressing down above you, and yet the space feels serene rather than crushing.

Since 1935, the caves have staged what may be the most atmospheric performance on the island. In an auditorium carved beside the lake, with room for more than a thousand visitors, the lights go down and a small ensemble — cello, harpsichord, and two violins — plays from rowing boats that slip across the water, each lit from within. The programme runs to gentle classical pieces, works by Chopin and Offenbach among them, and lasts only about ten minutes. In that setting, ten minutes is enough. The ritual has scarcely changed in spirit since the first musicians rowed out onto the lake, a tradition now older than most visitors' grandparents. When the last note fades, boats ferry visitors across the lake themselves, gliding out over the black water toward the daylight waiting at the exit.

The Caves of Drach sit just inland of Porto Cristo, a former fishermen's harbour in the municipality of Manacor, and they rank among the most visited attractions in all of Mallorca. That popularity is not merely a point of local pride. So many livelihoods along this stretch of the Llevant coast depend on the crowds the caves draw that any closure, however brief, lands like an omen; residents read a shuttered Drach as a warning sign for the whole local economy. For Porto Cristo and the wider municipality of Manacor, the caves are not a curiosity but a cornerstone. A cavern that took explorers sixteen years to fully chart has become, more than a century later, something the island quietly cannot do without.