Ellipse won't show in PictureBox

Hi,

I tried to create ellipse in a picturebox, but I don't know why the ellipse won't show.

Here is my code

        private int iMouseX = 0;
        private int iMouseY = 0;
        City city;
        List<City> cities = new List<City>();

        private void picMapTour_MouseMove(object sender, MouseEventArgs e)
        {
            iMouseX = e.X;
            iMouseY = e.Y;
        }

        private void picMapTour_MouseDown(object sender, MouseEventArgs e)
        {
            int x = iMouseX;
            int y = iMouseY;  
            city = new City(x, y);
            cities.Add(city);
            this.Invalidate();
        }

        private void picMapTour_Paint(object sender, PaintEventArgs e)
        {
            Graphics g = e.Graphics;
            foreach (var city in cities) 
            {
                g.FillEllipse(Brushes.Tan, (int)(city.X - 5), (int)(city.Y - 5), 10, 10);
                g.DrawEllipse(Pens.Red, (int)(city.X - 5), (int)(city.Y - 5), 10, 10); 
            }
        }

Can anyone help me where is the problem in my code?

Many Thanks :)