plain As a command 15 categories below plain Narrow by region 3 biome 2 flatland 2 geological-formation 2 natural-depression 2 alluvial-sediment 1 coastal-plain 1 environment 1 geographic-point 1 geographical-area 1 grassland 1 habitat 1 ocean-floor 1 river-mouth 1 sediment 1 substance 1 waterbody-bed 1 coastal-plain 1flatland 2abyssal-plainalluvial-flatfloodplainllanolowlandmoorpeneplainriver-deltasalt-flatsnowfieldsteppetidewatertundra