At the Earth's Core (Pellucidar #1)

At the Earth's Core by Edgar Rice Burroughs Cutting through the earth in an extraordinary burrowing device, David Innes and Abner Perry fear they may be incinerated in the planet's fiery core. Instead, they come upon Pellucidar - a savage, primordial world hidden several hundred miles beneath the earth's crust. There in an eerie, subterranean realm of vast oceans, lush jungles, and eternal noon, they encounter primitive humans and their beautiful, courageous queen, Dian.

At the Earth's Core is a 1914 fantasy novel by American writer Edgar Rice Burroughs, the first in his series about the fictional "hollow earth" land of Pellucidar. It first appeared as a four-part serial in All-Story Weekly from April 4-25, 1914

Excerpt:
"But when I saw these sleek, shiny carcasses shimmering in the sunlight as they emerged from the ocean, shaking their giant heads; when I saw the waters roll from their sinuous bodies in miniature waterfalls as they glided hither and thither, now upon the surface, now half submerged; as I saw them meet, open-mouthed, hissing and snorting, in their titanic and interminable warring I realized how futile is man’s poor, weak imagination by comparison with Nature’s incredible genius."