Ice ages are million-year periods of reduced global temperatures. Within each, glacial phases (maximum ice) alternate with interglacials (warm periods like the present), regulated by Milankovitch cycles.
The last glacial phase ended ~11,700 years ago. At its peak (~20,000 years ago), ice covered Scandinavia, northern Europe, and much of North America; sea level was 120 m lower. Spain was much colder and drier, with glaciers in the Pyrenees, Central System, and Sierra Nevada.