Updated: Oct 2
St. Mary is a Roman-Catholic church in the old Long Market in Gdansk, constructed in the 14th century. It is one of the largest brick churches in the world. Before the Second World War, it serves as a Lutheran church.
In fact, I was pretty disappointed. The building makes a great impression from the outside. However, the interior of the church isn't fancy and decorated like many other churches in Poland.
However, it is possible to climb (for a small entry fee) more than 400 stairs to the top of the tower for magnificent city views. I barely managed to climb it all, but I forgot all about it when I reached the top.
Climbing the Tower
Views From the Tower of St. Mary Basilica