About 1km roughly north of the Fundació Pilar i Joan Miró, in the satellite settlement of Gènova, you can poke about the stalactites and stalagmites of the Coves de Gènova. Discovered in 1906, the caves are not as interesting as the Coves del Drac in the east of the island, but are a pleasant enough distraction.
You reach a maximum depth of 36m and will be shown all sorts of fanciful, backlit shapes. The temperature is always around 20°C in the caves, and water has been dripping away for many millennia to create these natural 'sculptures'.