For four days straight, this city in the heart of Europe remained shut down as soldiers replace the Christmas Shoppers in Brussels. An eerie holiday feeling cloaks over Europe's Christmas Markets.

Fear of terrorist attack like the one in Paris has forced Brussels to raise alert to level 4, the highest it can go after arresting a total of 21 in a series of raids last weekend and on Monday as reported by Irish Independent. On a supposedly busy Monday, everything was closed.  The schools, museums, government offices, public transportations and market shops were all closed. Hospitals were putting off non-urgent consultations and events were cancelled. 

Wall Street Journal reports the recent event in Paris certainly cast a shadow of fear over the Christmas Markets. It has been a long tradition of Germans to drink mulled wine with family and friends at the annual Christmas markets. Over 50 million visitors flock the 2,500 markets every year according to the Federal Association of Fairground Showmen and Market Traders. According to the state government, Berlin alone already houses 60 seasonal markets. Operators are taking extra precautions since terrorists have targeted Christmas markets before.

In 2000, French and German police uncovered a terrorist plot to bomb the Christmas market in Strasbourg in France and in 2010, Germany warned citizens of plans for a possible terrorist strike in Christmas markets of potential targets.

The fact that Christmas markets are often held on large, open spaces with mazelike layouts and have no designated entry points unlike stadiums, security can be very challenging.

New York Times reports that Brussels Christmas market was supposedly scheduled to open on Friday according to Michel Vankeerberghen, an official with the Tourism Bureau for Wallonia. It is unclear whether the security lockdown would allow that to happen. Reports said situation will remain throughout the week. The gingerbread houses that were lined up have not yet opened.

Olivier Mees, the one who organizes Brussels' Christmas market said that the event usually attracts 1.5 million visitors, 300,000 of whom are tourists. Still, workers were putting up large decorations on the Boulevard Anspach, as soldiers in camouflage look on.

Most of the businesses in Brussels have seen a great decline in sales in the last four days.  Abdel Messaoudi who manages Pizza Hut said that revenues had fallen at least 75 percent since the city was put on high alert.

The ultimate search of the police raids was for Salah Abdeslam, a participant in the Paris terrorist attacks and who was living in Belgium. Police have already searched 24 homes in Brussels, detaining 21 people. 

It is still unclear how long the security lockdown will last. Workers are still preparing the Christmas market whether it will be opened or not.