public int MaximumScale {get;}

var levelCount = terrain.GetPyramidLevelCount();
IReadOnlyList<ArcGIS.Core.Data.Analyst3D.TerrainPyramidLevel> pyramidLevels = terrain.GetPyramidLevels();
foreach (var pyramidLevel in pyramidLevels)
{
  var resolution = pyramidLevel.Resolution;
  var maxScale = pyramidLevel.MaximumScale;
}