HELP! civiCRM Administration Area Not Showing! [Joomla 3.6.5] [civicrm 4.7.16]
You could try to go the page directly

www.yoursite.org/administrator/?option=com_civicrm&amp;task=civicrm/admin/setting/url&amp;reset=1

If you have sql access you could change them back.  They are stored in civicrm_settings

SELECT name, value FROM civicrm_setting WHERE group_name = "URL Preferences"


You'll see the url between quotes in the value field.