EARLY ADVENTURES IN HOLLOW EARTH
One of the enduring tropes of SF is the "Hollow Earth" concept, where the traveller encounters a subterranean world filled with monsters and (perhaps) beauteous maidens.
Although Edgar Rice Burroughs is renowned for this type of story, he is far from the originator of the idea.
Ludvig Holberg (1684-1754) was born in Bergen, Norway. His novel, written in Latin, "Niels Klim's Underworld Travels" tells of how the eponymous hero falls into a shaft near Bergen which transports him to the centre of the Earth, which has its own inner sun and system of planets. He falls on one called Nazar. Nazar is divided into different countries, and the one in which he lands is ruled by intelligent, walking trees (another first for Holberg). He travels throughout Nazar discovering strange customs such as one in which only the young are allowed to rule. In another, he is shocked to find sexual equality and campaigns to have females removed from public office. Eventually, the Nazarians tire of him and he is banished to the inner surface of the great void, which is inhabited by intelligent monkeys; one of whose females is desirous of mating with him. Fortunately, he falls into another shaft which has the opposite polarity and returns him to the surface where he discovers he has been away for 12 years.