Sri Subramanya Swamy Temple is one of the oldest Murugan temples in Bangalore. It is said to have existed since 800 years ago, and the idol in this shrine is identical to that in Thiruthani, one of the Six main abodes of Lord Muruga. The temple is located in Jogupalya near the Halasuru metro terminal. Here is the maps link.
Although the temple is in the middle of the city in a congested locality, it retains it's traditional look and calm ambiance.
The temple is also surrounded by spacious open area allowing plenty of parking.