If you are coming by flight, then Frankfurt and Manheim are the nearest airport and if you are coming by train then I think the above map will give you an idea about your travel route. A weekend is enough to explore and enjoy the city.
PLACE TO STAY:
There are two options. Either you can stay in the city itself. Or you can stay in Leimen, which is a neighboring town and very well connected with Heidelberg by bus. I stayed at a hotel in Leimen.
Heidelberg happens to be Germany’s oldest and famous university town. It is quite a small city crowned with its jewel, that is, the Heidelberg castle which is visible from every possible corner of the city. It is beautifully decorated with cobbled pathways, touristy German cafes and not to forget, river Neckar winding its way all through the city. Blessed with its picturesque scenery, it is actually a delight for nature lovers, hikers and bikers.
The city center is the best place to start your journey. As soon as you reach the center you will see tourist swamping from everywhere making the place pretty crowded and lively.
After the city center I headed towards Jesuitenkirche. This is a simple and pretty ordinary church as compared to the kind of churches one usually comes across in Europe, like Koln Cathedral