Is it safe to take taxi in Beijing or other cities

It's safe to take the legal taxis in these cities, however there are illegal taxis (known as black cars) that will charge you more money.  They will not use a meter and ask high prices for certain distances. Sometimes they even swap your money with fakes in order to extort more cash. Please prepare small amounts of money if you are taking taxis on your own.  Please also ask for the receipt from the taxi driver.  Most of the illegal taxis always stay around the airport or tourist attractions.  Please be vigilant in these circumstances.