If your website is using long URL like example.com/files/folder/sitemap.html, you can change it into "example.com/sitemap" in .htaccess
Note that this may take some tweaking and optimizing to get right and is unique to your application, so this is an example only. With that in mind, use the following .htaccess code sample to get you started with making the URLs look nice.
RewriteEngine on
RewriteRule ^sitemap/$ /files/folder/sitemap.html [L]