While there are a lot of Swaminarayan temples in Mumbai but Swaminarayan temple also called as the BAPS Swami Narayan Mandir is the most prominent amongst all the temples in Mumbai. The temple is located at swaminarayan chowk opposite Dadar Station and it is said that this place irrespective of the caste or religion gives the utmost peace and relaxation once you sit and pray in the premises.
The temple is around 100years old and is largely crowded by the Bhakts (worshippers) of Swami Narayan. Also the daily pujas at morning and evening are worth attending where locals attend in large numbers. Another prominent temple apart from this one is in Bhuleshwar in Mumbai but if you want to resist travelling too long, this is the temple you can surely get the divine blessings from!