Sahasrara Chakra – ‘one thousand’
The sahasrara chakra is located at the top of the head corresponding to the pineal gland in the physical body. This area is called the Brahmarandhra, or the “hole of Brahma.” At the time of death of an advanced yogi, the prana escapes the body through this hole. There are 1000 petals on this chakra, on which repeat the 50 letters of the Sanskrit alphabet. Sahasrara chakra is the abode of Siva.
When kundalini shakti reaches the sahasrara chakra the union of Siva and Shakti takes place. The active principal and the static principal unite. Individual consciousness and supreme consciousness become one and the yogi attains samadhi. Many mystical and religious traditions of the world describe this event with different names such as, nirvana, heaven, kaivalya, enlightenment, self-realization, etc.
“When Kundalina Shakti is united with Siva at the sahasrara, the yogi experiences extreme bliss. He attains the superconscious state and the highest knowledge. He becomes a fully developed jnani.” ~ Swami Vishnu-devananda, Meditation and Mantras
Some texts explain that the sahasrara is not a chakra in the same sense as the other chakras:
“Quote removed per request from Satyananda organization – copyright violation” ~ Swami Satyananda, Kundalini Tantra