India, April 15 -- A university city on the southern tip of the Netherlands, Maastricht is spread out over both sides of the Meuse River. Located about 215 km south of Amsterdam, this baroque beauty is known for its medieval-era architecture, cobbled streets, elegant squares, and vibrant cultural scene. It has the easy charm of a border town that has long blended Dutch, French, and Belgian influences, and every December, the city's Vrijthof Square becomes the heart of Magisch Maastricht (Magical Maastricht), a month-long celebration of lights, music, and markets.

But nothing is more magical than Maastricht's best-kept secret located in the midst of the old town: a doorway that most visitors typically mistake for a church. And technically...