In order to merge two or more column you need the \multicolumn
command, which takes three inputs:
\multicolumn{<number of columns you want to merge>}{<text alignement>}{<text>}
The desired table could be obtained with the following code:
\documentclass{article}
\usepackage{multirow}
\begin{document}
\begin{tabular}{|l|c|c|c|c|c|c|c|}
\hline
\multirow{2}{*}{} & \multicolumn{2}{c|}{Bronze Age} & \multicolumn{2}{c|}{Iron Age} & Hellenistic & \multicolumn{2}{c|}{Roman}\\
& \textbf{Kilise Tepe} & \textbf{Gordion} & \textbf{Kilise Tepe} & \textbf{Gordion} & \textbf{Ephesos} & \textbf{Ephesos} & \textbf{Salagassos}\\
\hline
\textbf{Presence of fish} & & + & & + & & & \\
\cline{1-1}
\multicolumn{1}{|c|}{\textbf{Marine species}} & & & & & & & \\
\cline{1-1}
\textit{Sardina pilcardus} & & & & & & & + \\
\cline{1-1}
\textit{Euthynnus alletteratus} & & & & & & & + \\
\hline
\end{tabular}
\end{document}
but, as AboAmmar pointed out in his answer, it will likely be too wide for the page. As an alternative to the rotating
package, you may consider using acronyms in order to decrease the width of every column, and add a legend (using once again the \multicolumn
command). For example:

\documentclass{article}
\usepackage{multirow}
\begin{document}
\begin{tabular}{|l|c|c|c|c|c|c|c|}
\hline
\multirow{2}{*}{} & \multicolumn{2}{c|}{Bronze Age} & \multicolumn{2}{c|}{Iron Age} & Hellenistic & \multicolumn{2}{c|}{Roman}\\
& \textbf{K. T.} & \textbf{G.} & \textbf{K. T.} & \textbf{G.} & \textbf{E.} & \textbf{E.} & \textbf{S.}\\
\hline
\textbf{Presence of fish} & & + & & + & & & \\
\cline{1-1}
\multicolumn{1}{|c|}{\textbf{Marine species}} & & & & & & & \\
\cline{1-1}
\textit{Sardina pilcardus} & & & & & & & + \\
\cline{1-1}
\textit{Euthynnus alletteratus} & & & & & & & + \\
\hline
\multicolumn{8}{l}{\textbf{K. T.}: Kilise Tepe}\\
\multicolumn{8}{l}{\textbf{G.}: Gordon}\\
\multicolumn{8}{l}{\textbf{E.}: Ephesos}\\
\multicolumn{8}{l}{\textbf{S.}: Salagassos}\\
\end{tabular}
\end{document}
Eventually, you may want to have a look at the booktabs
package, and remove some line from the table:

\documentclass{article}
\usepackage{multirow}
\usepackage{booktabs}
\begin{document}
\begin{tabular}{lccccccc}
\toprule
\multirow{2}{*}{} & \multicolumn{2}{c}{Bronze Age} & \multicolumn{2}{c}{Iron Age} & Hellenistic & \multicolumn{2}{c}{Roman}\\
& \textbf{K. T.} & \textbf{G.} & \textbf{K. T.} & \textbf{G.} & \textbf{E.} & \textbf{E.} & \textbf{S.}\\
\midrule
\textbf{Presence of fish} & & + & & + & & & \\
\cmidrule{1-1}
\multicolumn{1}{c}{\textbf{Marine species}} & & & & & & & \\
\cmidrule{1-1}
\textit{Sardina pilcardus} & & & & & & & + \\
\textit{Euthynnus alletteratus} & & & & & & & + \\
\bottomrule
\end{tabular}
\end{document}