Sinhagad Fort is easily accessible from Pune by road. The best seasons are monsoons and winters. There is a parking lot at the top where one can safely park the car and then explore the fort ruins by foot. As with most popular destinations, avoid the weekends. You get some of the most amazing bhajji (pyaaz ke pakore with garlic chutney) and jhunka – bhakri (a traditional Maharashtrian meal made of besan ki sabzi and bajre ki roti).
From Wikipedia: Sinhagad, Sinhgarh, or Sinhgad (Marathi for The Lion’s Fort), is a fortress located roughly 30 kilometres southwest of the city of Pune, India. Previously called Kondhana, the fort has been the site of many important battles, most notably the battle of Sinhagad in 1670. It was also strategically located at the centre of a string of other forts such as Rajgad, Purandar and Torna.
Perched on an isolated cliff of the Bhuleswar range of the Sahyadri Mountains, it is situated on a hill rising 1312 metres above sea level. Given natural protection by its very steep slopes, the walls and bastions were constructed at only key places; it has two gates – the Kalyan Darwaza in the south-east and the Pune Darwaza in the north-east.