Hello, If you're looking for one day trekking spots check out my profile for "Do-it-yourself one day trekking near Bangalore" You can tour one day in Bangalore by visiting Bangalore palace, Cubon park, Fun World, HAL aerodrome, etc. There is Mindful meditation and Jain temples which are must explore like Pyramid valley, and Jain temple near Anekal. Check out my profile for details. Happy Travel!
Here are a few spots to explore for a day in Bangalore
Cubbon park Lumbini gardens
Devanahalli fort You could make a plan to visit these places within Bangalore for a day. Nandi Hills
Anthargange are some places around you could cover.