Rauðhólar, also known as the "Red Mounds," are remnants of rootless cones in Reykjavík, Iceland. These reddish-colored rock formations were created when lava flowed over shallow lakes, causing explosions and forming unique craters. The cones are part of the Leitahraun lava flow from a shield volcano called Leitin, dating back about 5000 years. Today, Rauðhólar are protected as part of Reykjavík's nature reserve of Heiðmörk, making them a cool spot to check out if you're into geology and volcanic history.