Big cities usually have charm, brilliant and peculiarities. However a little caution and good sense is necessary to spend time in a amazing metropolis.
Carry less valuables you can.
Keep your passport safely stored.
Use your cameras and computers discreetly, don't show off lots of money, jewels or other objects that could gather the attention of thieves.
Always keep your stuff in physical contact with you, keep them on your front, unless they are locked in somewhere safe.
In the big cities, try to stay in the most touristic areas. If you want to see other parts of the city, Embratur can indicate a registered guide to escort you.