I would say going to Bhimashankar is worth going to for a one day trip especially if you think of it from a religious point of view.
Bhimashankar is located 100km away from Pune, so you can easily make it a day trip including seeing some places there. I would suggest leaving early to make most of the day.
Bhimashankar Temple
The main and important place to visit in Bhimashankar is the Bhimashankar Temple. It is one of the twelve Jyotirlinga shrines in India, and it has great important amoungst Shiv Ji devotees. The temple has some great architecture work and you are able to see some sculptors from ancient times.
Bhimashankar Wildlife Sanctuary
Bhimashankar Wildlife Sanctuary was created in 1984, so it is fairly new. It was created to guard the natural habitat of some animals and birds. When visiting the place you will be able to see the lush green surroundings and nature at its best.
Hanuman Lake
The Hanuman lake in Bhimashankar is worth a visit, it is a peaceful place where you can relax and ideal for a picnic spot. While at the lake you can see many bird and squirrels.