Vertically center a table on a landscape page

Question

I have a landscape page with one table on it. My current code horizontally centers the table, but how can I also vertically center it?

\documentclass[10pt,a4paper]{report}
\usepackage[latin1]{inputenc}
\usepackage[landscape]{geometry}
\usepackage[german]{babel}
\usepackage{lmodern}
\usepackage{adjustbox}

\begin{document}

\begin{adjustbox}{center}
 \resizebox{27cm}{!}{

  \begin{tabular}{|*7c|}
  \hline 
  \multicolumn{1}{|c|}{Column 1} &
  \multicolumn{2}{|c|}{Column 2} &
  \multicolumn{2}{|c|}{Column 3} &
  \multicolumn{2}{|c|}{Column 4} \\
  \hline
  1. Row & a & b & c & d & e & f \\ 
  \hline 
  % more lines here
  \end{tabular} 
 }

\end{adjustbox}

\end{document}

I omitted a the remaining rows here for the sake of clarity, but they don't occupy more than 50% of the page, so there is still plenty of space at the bottom. Putting the tabular in a table with \centering (as often suggested in that case) fails with Not in outer par mode. I assume that it's due to the adjustbox and resizebox.

Answer 1

\vspace*{\fill} before and after the adjustbox. You will perhaps have to add some additional \vspace to correct the difference in the margins.