The "ancestor" of the modern roller coaster was invented in Russia during the 17th and 18th centuries in the form of "Russian Mountains" (Russkie Gorki). These were massive wooden slides covered in ice that riders would descend on sleds. The invention of the "wheeled" version is often credited to Catherine the Great, who allegedly wanted to enjoy the thrills of the ice slides during the summer months. She commissioned a summer version at her Oranienbaum estate in the 1780s, which featured carts with wheels that locked into grooved tracks—a critical engineering step toward the modern coaster. The technical design of these early wheeled structures was overseen by the Russian scientist and engineer Andrey Nartov. When French travelers saw these "Russian Mountains," they brought the idea back to France, where the first "centrifugal" and "circuit" coasters were developed, but the foundational concept of a gravity-driven "thrill ride" remains a Russian innovation.