Set out for a spiritual excursion that takes you to 2 of Spain's most striking religious sites—the mountain monastery of Montserrat and Gaudí's unfinished Sagrada Familia in the heart of Barcelona. With a private guide leading the way, delve into the past, present, and future of these one-of-a-kind places of worship.

Pick a time that works for you and meet your guide, starting at the Sagrada Familia or heading out to Montserrat first depending on your schedule. At the Sagrada Familia, take in the majestic towers and impressive height of the church's exterior, noting how modernist and neo-Gothic features combine to create a structure like no other. Then, skip the long lines and head inside, gazing up at the organic shapes of the light-filled nave and the shimmering stained-glass windows as your guide describes the city's plans and schedule for completing architect Antoni Gaudí's final masterpiece.

From there, venture out of the city and head for the hills, arriving at the remote monastic retreat of Montserrat. Set amid the craggy peaks of a saw-like mountain range, this pilgrimage site's dramatic natural setting is sure to take your breath away. Spend some time exploring the area, riding a funicular up to higher heights if you want to trek around the nature trails, visiting the basilica to see the famed black Madonna, or catching a performance by the monastery's celebrated boys' choir before the return ride to Barcelona.