WordPress/wp-content/themes/twentyten/attachment.php

<?php
/**
 * Template for displaying attachments
 *
 * @package WordPress
 * @subpackage Twenty_Ten
 * @since Twenty Ten 1.0
 */

get_header(); ?>

		<div id="container" class="single-attachment">
			<div id="content" role="main">

			<?php
			/*
			 * Run the loop to output the attachment.
			 * If you want to overload this in a child theme then include a file
			 * called loop-attachment.php and that will be used instead.
			 */
			get_template_part( 'loop', 'attachment' );
			?>

			</div><!-- #content -->
		</div><!-- #container -->

<?php get_footer(); ?>