In order to understand the Ascension, we first need to know something about the Spiritual Journey of the Sufi.
Take a look at the video below.

(From "Percy Jackson and the Olympians: The Lightning Thief." Copyright Twentieth Century Fox, 2010.)

The Empire State Building in Manhattan, New York, was long considered the tallest building in the world. Here, in the space of seconds, we see the Spiritual Journey (which can take many years and even a lifetime) encapsulated in a nutshell. Our hero, the Traveler, enters the Path. He walks on the Straight Path until he encounters the Gatekeeper (night guard), who is also the Teacher. The Master looks him over. If he is found worthy, the Teacher gives him the keys that will enable him to reach Floor Omega, which lies beyond physical space. Although not depicted in the video, the disciple continues to walk the Straight Path until he reaches the elevator. This part of his journey can also be likened to the horizontal leg of the Prophet’s Ascension, his trip from Mecca to Jerusalem. When the time comes, the Ascension in the vertical direction (orthogonal to all dimensions) begins.

Below is another symbolic/metaphorical depiction of an Ascension (meeraj). Please bear in mind that such an Ascension is not physical (in three dimensions) but spiritual.

(from Walt Disney's "Atlantis: The Lost Empire")

(Copyright Walt Disney Productions, 2001.)

Or double-click below to view full screen:

By loving God, by befriending God (wali: Friend of God or Saint, plural awliya), by obeying His instructions and shunning His prohibitions, the heroine draws closer to God, until she becomes the recipient of Divine Attraction (jazba). She undergoes an Ascension (meeraj) in which she is "beamed up" to God, resulting in Attainment/Joining/Union (wuslat). There have been many woman Saints in Islam, among whom the most famous is Rabia al-Adawiya.

The central core symbolizes the Essence (Zat) of God, who is Light (Koran 24:35). It also symbolizes His Absolute Unity (Ahadiyah or Wahdah). The stone slabs circulating the core are the "masks of God": they symbolize His Attributes (Sifat), after which His Names (Asma) are named. The Attributes (and thus, Names) proceed ("emanate") from the Essence of Absolute Unity. Since they constitute the beginning of Multiplicity, this stage of the Descent is termed Wahidiyah or Wahdaniyah. From these, in turn, proceed the myriad creatures in the universe, constituting Multiplicity (kasrah).

After Absorption into the Godhead (Annihilation in God, called fana fi Allah by the Sufis), the heroine returns to the world (baqa bi Allah). She is, however, totally transformed (tabdil, whence comes abdal), and has reached a condition totally incomparable to anything else in the universe. She has attained a state of Divine Perfection (kamal), and become a Perfect Human Being (insan al-kaamil).