Upon recommendation from our Heidelberg Castle tour guide, we went directly to the Philosopher’s Walk after visiting the Castle and town to try to catch the Castle at sunset from the Walk.
The Philosopher’s Walk is a well-mainained path that runs from the newer part of town and ends with steep stairs down to the Alte Brücke (or you can turnaround if you are mobility inclined, or just want to avoid the steps!). Our castle tour guide recommended starting the tour in the newer part of town so that we would be looking at the castle the entire walk (and not back at the castle), but we started at the Alte Brücke, because it was closer to the Castle, and ended in the new town, very close to our dinner spot – Dorfschänke!
The stairs near the Alte Brücke are not scary (I hate heights!) or that tough, but it was steep – bring water. At the top of the hill, there are great views of the Castle and the old town. The path is pretty level after the hill and ends in the new part of down after walking by some gorgeous homes.
The Philosopher’s Walk is entirely free. However, it is not worth it at all if it is raining. I would allow at least an hour for the entire Philosopher’s Walk.