riemann_log

	       \begin{tikzpicture}
		 \draw plot[smooth cycle]
		 coordinates{
		 (-10:2cm)
		 (0:3cm) (30:3cm) (60:3cm) (90:3cm) (120:3cm) (150:3cm) (180:3cm) (210:3cm) (240:3cm) (270:3cm) (300:3cm) (330:3cm) (360:3cm)
		 (10:2cm)
		 (360:1cm) (330:1cm) (300:1cm) (270:1cm) (240:1cm) (210:1cm) (180:1cm) (150:1cm) (120:1cm) (90:1cm) (60:1cm) (30:1cm) (0:1cm)
		 };
		
	       \end{tikzpicture}