Source: UNESCO World Heritage
Postcard 1 - Hungary
Baradla Cave of Aggtelek Karst in north east of Hungary at the Slovakian border. Nice stamps used. Thanks to Rita of Hungary.
Slovakia Caves of Ochtinska aragonitova jaskyna. Thanks to Radek of Czech Republic.
Postcard 2B - Slovakia
Dobsina Ice Cave, a UNESCO World Heritage site in Slovakia. Thanks to Rita for mailing from Slovakia.