Lithuania does not have high mountains and its landscape is dominated by blooming meadows, dense forests and fertile fields of cereals. However it stands out by the abundance of hillforts, which previously had castles where the ancient Lithuanians burned altars for pagan gods. Lithuania is a particularly watered region with more than 3,000 lakes, mostly in the northeast. The country is also drained by numerous rivers, most notably the longest Nemunas. Lithuania is home to two terrestrial ecoregions: Central European mixed forests and Sarmatic mixed forests.