Montserrat is a mountain top monastery in Catalonia, Spain. Situated atop an unusual rock mountain, it is very popular among Catalans, and Catholic pilgrims come from far and wide to see the Black Madonna.
The monastery is Catalonia's most important religious retreat and groups of young people from Barcelona and all over Catalonia make overnight hikes at least once in their lives to watch the sunrise from the heights of Montserrat.
At 1236 meters (4055 ft) above the valley floor, Montserrat is the highest point of the Catalan lowlands, and stands central to the most populated part of Catalonia. The stone monolith is ideally located to play an important role in the cultural and spiritual life of Catalonia.
Link to official site of Montserrat: 
By train + cable car
Travelling from Barcelona, take Ferrocarrils de la Generalitat (R5 Line) train from Plaça d'Espanya to Montserrat-Aeri. Trains run every hour, combined return adult ticket costs 18,80€. Trans montserrat tickets for adult costs 24,40€.
From Montserrat-Aeri, take the cable car up.
By train + Funicular
Similarly to the previous option take the same R5 Line train from Plaça d'Espanya, Barcelona but to the next stop: at Monistrol de Montserrat you can change for the funicular railway (Cremallera de Montserrat). Combined return adult ticket costs €20 (including the funicular to Montserrat Monastery). Total travel time is 90 minutes one way (Placa d'Espanya-Monserrat Monastery). Last funicular runs at 18:15 downhill.
Perhaps not as scenic as the cablecar, but cheaper, and users get first choice of seats on the R5 for the journey back to Barcelona - cable car users get on one stop later.
Buses from Barcelona leave from the Plaça de la Universitat in the morning.
By private taxi transportation
Private transport is for sure the most confortable option to get to Montserrat easy and fast. There are several companies who offer this kind of service for smaller and for bigger groups.
The only way to get around the Montserrat monastery complex is on foot (it's not too big though!)
Look around the impressive buildings
Monastery and The Black Virgin of Montserrat
Santa Maria de Montserrat is a Benedictine abbey which hosts the Virgin of Montserrat, and the Publicacions de l'Abadia de Montserrat, a publishing house, the oldest press in the world, still running, with the first book published in 1499.
The Virgin of Montserrat  is a statue of the Virgin Mary and infant Christ venerated at the Santa Maria de Montserrat  monastery. Virgin of Montserrat (the black virgin), is Catalonia's favourite saint, and is located in the sanctuary of the Mare de Deu de Montserrat.
It is one of the black Madonnas of Europe, hence its familiar Catalan name, la Moreneta ("The little dark-skinned one"). Believed by some to have been carved in Jerusalem in the early days of the church, it is a Romanesque sculpture in wood from the late 12th century. Legend has it that the Benedictine monks could not move the statue to construct their monastery, choosing to instead build around it. The statue's sanctuary is located at the rear of the chapel, where an altar of gold surrounds the icon, and is now a site of pilgrimage. Lady of Montserrat
In 1844, Pope Leo XIII declared the virgin of Montserrat patroness of Catalonia.
L'Escolania choir  school is a boys' choir of sopranos and altos based at the Benedictine abbey Santa Maria de Montserrat. When the repertory requires it, they are accompanied by the Montserrat Chapel Choir, composed of old choirboys and the monks of the Ministry Chapel Choir.
L'Escolania sings every day in the Basilica of Montserrat, often to a great affluence of pilgrims and visitors from all over the world. The midday Salve has become, over the past decades, the most visited daily act of the Sanctuary. The Escolania, Montserrat’s Boys’ Choir, is one of the oldest in Europe, and performs during religious ceremonies and communal prayers in the basilica.
Enjoy the fantastic views over the local landscape
Places to eat at Montserrat are limited and expensive but of high quality and good meal choices (cafeteria style), so it's a great idea to bring your own lunch. If you're coming from Barcelona, a good plan is to get up early and head to La Boqueria, the big open market near the head of Las Ramblas, to stock up on sandwich/snack fixin's - bread, cheese, meat, olives, wine, etc.. Pack it up and bring it with you. Mmm...
The marketplace also offers many delectable homemade goods sold by locals, including canned honey, pastries, preserves, cured meat and candy. Also what can be bought is 2 cheeses that is provided only in Montserrat.
Montserrat is a very large summit, although the town is relatively safe and tourist-friendly, it can be very dangerous for hiking as much of it is unchartered woodland. By all means, if you are traveling with a group, do not stray from them if you decide to go hiking. If you find out that someone has strayed from your group, summon the local authorities.