Can someone explain how to fix this error when trying to add a picture?

Question

I am trying to add a picture using:

\begin{figure}[!h!t]
    \centering
        \includegraphics[width=90mm]{Hollywood and Beverly Hills}
    \caption{Hollywood and Beverly Hills}
    \label{fig: h&bh}
\end{figure} 

but am getting the error:

! Argument of \@xfloat has an extra }.
<inserted text> 
                \par 
l.15 \begin{figure}[!h!t]

?

I want it so that the picture appears at the beginning of the document in a section that is not twocolumn, so I tried using two @columnfalse but I can't get it to work.

Here is a minimal example of my document:

\documentclass[twocolumn,12pt]{article}
\usepackage{graphicx}
\usepackage{setspace}
\doublespacing

\begin{document}

\pagestyle{plain}
\twocolumn[
\begin{@twocolumnfalse}
\begin{center}
\section*{Neighborhoods}
\end{center}


\begin{figure}[!h!t]
    \centering
        \includegraphics[width=90mm]{neighborhoods}
    \caption{Hollywood and Beverly Hills}
    \label{fig: hbh}
\end{figure} 

\vspace{.25 in}
\end{@twocolumnfalse}]

\section*{Hollywood}

\section*{Beverly Hills}

\end{document}

Can someone help me fix this?

Answer 1

You can not have a floating environment inside the optional argument of \twocolumn also you need to hide inner [] from any LaTeX optional argument by using a brace group. [{... [...]...}]

\documentclass[twocolumn,12pt]{article}
\usepackage[demo]{graphicx}% [demo] as I have not got the figure
\usepackage{setspace}
\doublespacing
\usepackage{capt-of}

\begin{document}

\pagestyle{plain}
\twocolumn[{

\section*{Neighborhoods}

    \centering
        \includegraphics[width=90mm]{neighborhoods}
    \captionof{figure}{Hollywood and Beverly Hills}
    \label{fig: hbh}

\vspace{.25 in}
}]

\section*{Hollywood}

\section*{Beverly Hills}

\end{document}

Answer 2

The \twocolumn macro looks for an optional argument by checking if the next token is [. Therefore the rogue [ after \twocolumn upsets LaTeX enormously. Delete it, and your document will (probably) compile.