I think it is members' only.
There are similar mysterious entrances in several parts of RuneScape; you need a certain level of Dungeoneering in each case. Also, some of those entrances are for members only.
Leela's father is Osman. Osman can be found near the entrance of the Al-Kharid palace, which is near to the Al-Kharid bank.
he is in al kharid
Osman is a NPC who can be found north of the palace in Al-Kharid. He calls himself the "Spy Master of Al Kharid".
From a stall NPC in Al-Kharid
al kharid duel arena
There is a mine that is southwest of Al Kharid. You can mine it there
Osman can be found north of the palace in Al-Kharid.
Next to Al-Kharid Desert Palace.
There's one in Al Kharid and in Rimmington.
Above the Duel Arena in Al-Kharid.
He is in Al-Kharid *answer needs updated