How to get base admin Magento url?

Question

It should be trivial, but cannot find a correct way. Even if default is "/admin" I would like not to hardcode as it might change in future.

Obviously, these variants are incorrect:

Mage::getUrl('admin');
Mage::helper('adminhtml')->getUrl('admin');

UPD: It seems some clarification is needed. Right now I have this url to my admin panel:
http://sample.com/admin
but later I might have to change it to
http://sample.com/backend
and would like to keep my link generating code untouched.

Answer 1

echo Mage::helper('adminhtml');

Answer 2

From the following url you will find different way to get Admin specific url http://www.codexpedia.com/magento/magento-getting-the-admin-panel-urls/

Answer 3

try this

Mage::getUrl('adminhtml');