The extinct bear from Ice Age Eurasia that lived in caves and could exceed the size of modern brown bears was the cave bear.
The cave bear, Ursus spelaeus, lived across much of Europe and parts of Asia during the Pleistocene. It became extinct roughly 24,000 years ago, near the Last Glacial Maximum. Its remains are especially common in caves, which gave the animal its name. Caves were probably important hibernation sites, although cave bears also foraged outside them.
Cave bears could reach about 2 meters in length, with males commonly weighing several hundred kilograms. Their broad, domed skulls and powerful limbs made them look similar to brown bears, but they were generally more specialized for plant-based diets. Fossil evidence suggests they were largely or almost entirely herbivorous.
A common mix-up is the short-faced bear, which was a different extinct bear known mainly from North America. Cave bears were related to brown bears and polar bears, but they were not simply oversized brown bears; they followed a distinct evolutionary branch and may represent several closely related species.