For all organized group visits, a written reservation is required at: presentacija@pp-medvednica.hr A minimum of 20 people is considered a group. For children under the age of 12, it is mandatory to enter and stay accompanied by an adult during the whole visit to Veternica Cave or Zrinski Mine. The right to enter with a pass is granted to Croatian nationals and disabled civilians, as well as persons accompanying a disabled person who need someone else's care and assistance for their regular life, upon presentation of an identity card or a certificate of recognized status. The right to enter with a pass is granted to tour guides and companions of organized groups upon presentation of an ID card or certificate of recognized status, as well as teachers, educators and teaching assistants accompanying school groups and kindergarten groups. The deadline for canceling an announced visit is at least 48 hours before the scheduled appointment, otherwise the Public Institution reserves the right to charge the reserved service in full.