Kali is known as wife of Lord Shiva. Kali is another form of Parbati, is very dreadful Goddess. Devotees of Kali sacrifice the Male goat at the temple. The best day to worship Kali is Tuesday or Saturday. Most of devotees of Kali go to temple on Saturday to worship.
The area of Kali Temple is mixed with Hindus, Buddhists and Christians. so you van enjoy the mixed culture of Nepali people at the same place.
It's more like a sabbatical break trip for those who has keen interest on culture, it's practice. To feel the symbolic meaning of culture and the nature, this trip is very interesting.