\usetikzlibrary{calc,trees,positioning,arrows,chains,shapes.geometric,%
decorations.pathreplacing,decorations.pathmorphing,shapes,%
matrix,shapes.symbols,plotmarks,decorations.markings,shadows,backgrounds}


\pgfdeclarelayer{background}
\pgfdeclarelayer{foreground}
\pgfdeclarelayer{L0}
\pgfdeclarelayer{L1}
\pgfdeclarelayer{L2}
\pgfdeclarelayer{L3}
\pgfsetlayers{background,L0,L1,L2,L3,main,foreground}

\newcommand{\scale}{0.15}

\begin{tikzpicture}[scale=\scale,every node/.style={scale=\scale},on grid ]

	\tikzstyle{LostMB}=[black, thick]
	\tikzstyle{ExtrapolatedMB}=[black, dashed, thick]
	\tikzstyle{TextNode}=[scale=4.2, text centered, text width=3.3cm]
	\tikzstyle{SymbolNode}=[scale=5.2, text centered]

	\newcommand{\gridsize}{30}
	%\draw[help lines] (-\gridsize,-\gridsize) grid ++(\gridsize*2,\gridsize*2);

	\draw[LostMB] (0,0) rectangle ++(8,8);

    \draw[ExtrapolatedMB] (6-16,6) rectangle ++(16cm,16cm);
	\draw[ExtrapolatedMB] (4,4) rectangle ++(16cm,16cm);
	\draw[ExtrapolatedMB] (6,-14) rectangle ++(16cm,16cm);
	\draw[ExtrapolatedMB] (3-16,-14) rectangle ++(16cm,16cm);

	\node[TextNode](EMB1) at (5-16+16/2,7+16/2) {Extrapolated PU$_1$};
	\node[TextNode](EMB1) at (5+16/2,4+16/2) {Extrapolated PU$_2$};
	\node[TextNode](EMB1) at (6+16/2,-14+16/2) {Extrapolated PU$_4$};
	\node[TextNode](EMB1) at (3-16+16/2,-14+16/2) {Extrapolated PU$_3$};

	\node[SymbolNode] at (2,1) {$\circ$};
	\node[SymbolNode] at (7,1) {$\circ$};
	\node[SymbolNode] at (7,7) {$\circ$};
	\node[SymbolNode] at (5,7) {$\diamond$};
    \node[SymbolNode,scale=0.7] at (2,4) {$\bigtriangleup$};
    \node[SymbolNode] at (-2,4) {$\star$};

\end{tikzpicture}