Min­ers first dis­cov­ered the Cave of Swords, locat­ed direct­ly above the Cave of the Crys­tals, in 1910. The crys­tals there are much small­er than in the Cave of the Crys­tals (a mere 1–2 meters ver­sus a whop­ping 12 metres!), and the tem­per­a­ture is cool, which may be why the crys­tals stopped grow­ing.