Q: You are given a passage. You need to construct a question about the information present in the passage. Construct a question in such a way that (i) it is unambiguous, (ii) its answer is the whole paragraph. Avoid creating questions that can be answered correctly without actually understanding the paragraph.
In the 7th century a monk from Crediton, Devonshire, went to Germany to teach the Word of God. He did many good works there, and spent much time in Thuringia, an area which was to become the cradle of the Christmas Decoration Industry.

Legend has it that he used the triangular shape of the Fir Tree to describe the Holy Trinity of God the Father, Son and Holy Spirit. The converted people began to revere the Fir tree as God's Tree, as they had previously revered the Oak. By the 12th century it was being hung, upside-down, from ceilings at Christmastime in Central Europe, as a symbol of Christianity.

The first decorated tree was at Riga in Latvia, in 1510. In the early 16th century, Martin Luther is said to have decorated a small Christmas Tree with candles, to show his children how the stars twinkled through the dark night.
A:
Where did the tradition of Christmas trees start?