Hi care! Welcome to our Spain-loving message board!!
Since you posted in the Safety & Security Issues forum I'm guessing you're asking about your safety during New Year's Eve in Madrid.
There are A LOT of people in the city during New Year's Eve, particularly in Puerta del Sol. This area is PACKED with people like sardines and pickpocketing exists but is by no means rampant. Just be careful and carry all valuables under your coat and/or in front pockets and not in purses.
Otherwise, away from Puerta del Sol maybe Plaza Mayor where there are always a lot of people during the Christmas/New Years Holiday, you won't have much worry. As usual, be careful walking down empty back streets (which, I'd guess would be hard to find in Madrid on New Years Eve - EMPTY, that is). Just be smart. Violent crimes aren't common thank goodness.
Have fun! Saludos, MadridMan
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