public RadForm1()
        {
            InitializeComponent(); new RadControlSpyForm().Show();

            RadMapElement.VisualElementFactory = new MyMapVisualElementFactory();

            OpenStreetMapProvider osmProvider = new OpenStreetMapProvider();
            MapTileDownloader tileDownloader = osmProvider.TileDownloader as MapTileDownloader;
            tileDownloader.WebHeaders.Add(System.Net.HttpRequestHeader.UserAgent, "your application name");
            osmProvider.EnableCaching = false;
            this.radMap1.MapElement.Providers.Add(osmProvider);

            MapLayer easternLayer = new MapLayer("CitiesLayer");
            this.radMap1.Layers.Add(easternLayer);

            MapPin element = new MapPin(new PointG(40.4467648, -80.01576030));
            element.Text = "Pittsburgh";
            element.BackColor = Color.Red;
            this.radMap1.Layers["CitiesLayer"].Add(element);
            element = new MapPin(new PointG(40.8130697, -74.07439790));
            element.Text = "New York";
            element.BackColor = Color.Green;
            this.radMap1.Layers["CitiesLayer"].Add(element);
            element = new MapPin(new PointG(42.3665137, -71.06160420));
            element.Text = "Boston";
            element.BackColor = Color.Blue;
            this.radMap1.Layers["CitiesLayer"].Add(element);
            element = new MapPin(new PointG(43.6434661, -79.37909890));
            element.Text = "Toronto";
            element.BackColor = Color.Yellow;
            this.radMap1.Layers["CitiesLayer"].Add(element);

            this.radMap1.Layers[0].ClusterStrategy = new DistanceClusterStrategy();
            this.radMap1.Layers["CitiesLayer"].ClusterDistance = 200;
        }

        public class CustomMapCluster : MapCluster
        {
            public override void Paint(Telerik.WinControls.Paint.IGraphics graphics, IMapViewport viewport)
            {
                Graphics g = graphics.UnderlayGraphics as Graphics;

                long mapSize = MapTileSystemHelper.MapSize(viewport.ZoomLevel);
                object state = graphics.SaveState();
                g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.AntiAlias;
                graphics.TranslateTransform(this.drawRect.X, this.drawRect.Y);

                for (int i = -1; i < viewport.NumberOfWraparounds; i++)
                {
                    Rectangle rect = new Rectangle((int)(-this.drawRect.Width / 2L + i * mapSize), 
                        (int)(-this.drawRect.Height / 2L), (int)this.drawRect.Width, (int)this.drawRect.Height);
                    GraphicsPath path = new GraphicsPath();
                    path.AddEllipse(rect);

                    FillPrimitiveImpl fill = new FillPrimitiveImpl(this, null);
                    fill.PaintFill(graphics, path, rect);

                    BorderPrimitiveImpl border = new BorderPrimitiveImpl(this, null);
                    border.PaintBorder(graphics, null, path, rect);

                    StringFormat stringformat = new StringFormat();
                    stringformat.Alignment = TelerikAlignHelper.TranslateAlignment(ContentAlignment.MiddleCenter);
                    stringformat.LineAlignment = TelerikAlignHelper.TranslateLineAlignment(ContentAlignment.MiddleCenter);
                    graphics.DrawString(
                        this.ClusteredItems.Count.ToString(),
                        rect,
                        this.Font,
                        this.ForeColor,
                        stringformat,
                        Orientation.Horizontal,
                        false);
                }

                graphics.RestoreState(state);
            }
        }

        public class MyMapVisualElementFactory : MapVisualElementFactory
        {
            public override MapCluster CreateCluster()
            {
                return new CustomMapCluster();
            }
        }