\documentclass[a4paper]{article}
\usepackage{german}
\usepackage[utf8]{inputenc}

\usepackage{pgfplots}

\usepackage{pgfplotstable}
\usepackage{booktabs}
\usepackage{array}
\usepackage{colortbl}

\pgfplotsset{compat=1.3}

\begin{document}

\begin{tikzpicture}
	\begin{axis}[colorbar,view={0}{90}]
	\addplot3[contour gnuplot={levels={0,10}}] {x^2-y^2};
	\end{axis}
\end{tikzpicture}
\end{document}

