Illiyyeen عِلّيين or Illiyyoo عِلّيّون is from the highest places in the Paradise.
Allah (SWT) says in Quran : (Nay, verily, the record of of deeds of the most pious (Al-Abrar) is in Illiyyeen, and how do you know what is Illiyyoon) (Sura Al-Mutaffiffeen, verses 18 and 19).
Abu Hamza al-Thimaali narrated that he heard Imam Al-Baqir (AS) saying: Allah has created us (Ahlul Bayt) from Illiyyeen and created the hearts of our Shia from it, then created their bodies from lower than that.) (Basaa'ir al-Darajaat, page 5).
Wassalam.