The view of this church (we're told that "Tyn" is correctly pronounced "Teen") from the Old Town Square is plain spectacular. Part of the front of the church is hidden from view by the building in front of it. I think this is what leads to confusion about where the entrance is.
To find the entrance, stand in the Old Town Square and face the church. At the ground level, you'll see a café and several openings. Take the leftmost opening and you'll enter a tunnel-like passage way. This leads to the opening of the church.
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