If we limit our discussion within Natural beauties(i.e.,excluding Monuments,Tombs,Memorials,Forts,temples & other Man Made Marvels),then there is only few UNESCO World heritage Sites in India:They're
(i)Kaziranga Wild Life Sanctuary, Assam(nearest Rail Head :Golaghat,Assam)
(ii)Manas Wild Life Sanctuary, Assam(nearest Rail Head:Barpeta Road,Assam)
(iii)Keoladeo National Park(Nearest RailHead:Bharatpur,Rajasthan)
(iv)Sundarbans...
more... National Park(Nearest Rail Head:Sealdah,West bengal)
(v)Nanda Devi and Valley of Flowers National Parks(nearest Rail Head:Kathgodum,Uttarakhand)
(vi)darjeeling Himalayan Railway(Nearest Rail Head:new Jalpaiguri,West Bengal)