view of pivka river park near postojna cave entrance at nice winter day slovenia

architecture beautiful bright building cave day destination entrance holidays jama karst mountain nice outdoor postojna postojnska sightseeing slovenia snow system travel trip underworld vacations view white winter tourists environment geology attraction attractive europe landmark landscape visiting country top tourist february site season traditional tourism sunny tour excursion group underground scenery nature natural vacation pivka river planina unica confluence subterranean confluences valley cold weather trees park birds bird duck wild ducks riverbed flowing flow shore banks alley resort hotel tourism