If you didn't bring sandwiches with you, we recommend making a pit stop at La Plata bar (at the end of the street leading to the rack railway) and buying some sandwiches (4.70€) and water or soft drinks (1.40€) for a picnic on the top of Montserrat.
Take the Sant Joan funicular (follow the signs in front of the information office) to the top. It leaves every 20 minutes (see timetable) and takes 10 minutes.
Check out the viewpoint above the station. There you'll find an exhibition room (Aula de la Natura) that explains the entire history of Montserrat (highly recommended) and a viewpoint with a map of the different rocks of Montserrat suggesting what each one looks like.
Exiting the station, on the right, we recommend following part of the Sant Geroni path to the viewpoint with iron railings (15 minutes). The views of the monastery from here are stunning. You can also see rock climbers scaling the mountain. When you get here, return to the funicular (15 minutes).
If you want to keep walking, on the left, when exiting the funicular, you'll find a path that leads to the monastery (45 minutes). The path is mildly intense: the first hill is quite steep and the rest of the way is downhill along occasionally narrow trails. After about 20 minutes, you'll come to the Cruz de Sant Miquel Viewpoint with great views of the landscape.
If, on the other hand, your feet are tired, take the funicular directly back to the monastery.