An expert on Antoni Gaudí reveals what the Modernista architect had envisioned for Barcelona's magnificent Sagrada Família church, and shares updates on the work to complete what Gaudí started 135 years ago. And travel writer Seth Kugel makes the case for letting serendipity play a role in your trip’s itinerary.

• Historian and tour guide Gijs van Hensbergen, author of "The Sagrada Família" (Bloomsbury)
• Travel writer Seth Kugel, author of "Rediscovering Travel" (Liveright - W.W. Norton)

• Gijs van Hensbergen writes about Antoni Gaudí and the building of the Sagrada Familia church in his book "The Sagrada Família."
• The Sagrada Família in Barcelona maintains a construction blog online.  
• A guide to 20 Gaudí sites in Barcelona.
• Seth Kugel is the author of "Rediscovering Travel: A Guide for the Globally Curious."
• Seth writes a blog of travel tips on his website.  He also writes about increasing a sense of spontaneity in your travels for the New York Times.