I asked a question about this before, and got most of it fixed.    If I switch off https redirect and go to http://mydomain.com/svn/test0, I get the authentication window popping up, and I can enter my AD credentials, and bingo.   Switching https redirect back on, if I go to http://mydomain.com I am automatically redirected to https, which is what I want, and the 'CerntOS test page' pops up.  Perfect.  
The problem occurs when I want to go to one of my test repos via https.  Here is my httpd.conf file, with confidential information suitably hosed... 
===
NameVirtualHost *:80
<VirtualHost *:80>
        ServerAdmin 
[email protected]
        ServerName 
svn.mycompany.com
        ErrorLog logs/subversion-error_log
        CustomLog logs/subversion-access_log common
        Redirect permanent / https://svn.mycompany.com
</VirtualHost>
<VirtualHost 
svn.mycompany.com:443>
        SSLEngine On
        SSLCertificateFile /etc/httpd/ssl/wildcard.mycompany.com.crt
        SSLCertificateKeyFile /etc/httpd/ssl/wildcard.mycompany.com.key
        SSLCertificateChainFile /etc/httpd/ssl/intermediate.crt
        ServerName 
svn.mycompany.com
        ServerAdmin 
[email protected]
        ErrorLog logs/subversion-error_log
        CustomLog logs/subversion-access_log common
<Location /svn>
        DAV 
svn
        SVNParentPath /usr/local/subversion
        SVNListParentPath off
        AuthName "Subversion Repositories"
# NT Logon Details
        Require valid-user
        AuthBasicProvider file ldap
        AuthType Basic
        AuthzLDAPAuthoritative off
        AuthUserFile /etc/httpd/conf/svnpasswd
        AuthName "Subversion Server II"
        AuthLDAPURL "ldap://our-pdc:389/OU=Company Name,DC=com,DC=co,DC=uk?sAMAccountName?sub?(objectClass=*)"
        AuthLDAPBindDN "DOMAIN\subversion"
        AuthLDAPBindPassword XXXXXXX
        AuthzSVNAccessFile /etc/httpd/conf/svnaccessfile
</Location>
</VirtualHost>
===
Now, in ssl_error_log, I get 
===
==> /etc/httpd/logs/ssl_error_log <==
[Fri Nov 01 16:07:55 2013] [error] [client XXX.XXX.XXX.XXX] File does not exist: /var/www/html/svn
===
This comes from the DocumentRoot directive further up the httpd.conf file, which of course points to /var/www/html.  I know that this location is wrong, but how can I get 
SVN to serve the repo?
I tried an Alias directive as so .. 
Alias /svn /usr/local/subversion
.. but this didn't work.  I tried to alter the Location directive. That didn't work either.
Can someone help?  I sense that this is so close to being solved ... 
Thanks.
Edit: apachectl -S output:
[root@svn conf]# apachectl -S
VirtualHost configuration:
127.0.0.1:443 
svn.mycompany.com (/etc/httpd/conf/httpd.conf:1020) 
wildcard NameVirtualHosts and default servers:
default:443 
svn.mycompany.com (/etc/httpd/conf.d/ssl.conf:74)
*:80 is a NameVirtualHost
default server 
svn.mycompany.com (/etc/httpd/conf/httpd.conf:1012)
port 80 namevhost 
svn.mycompany.com (/etc/httpd/conf/httpd.conf:1012)
Syntax OK