If you want to trade bitcoin then you can choose large and reputable trading floors such as floor trading floor has many strengths and safety for the trader you can find trading with the floor and you Can be assured when trading here
Your question is not clear. People are confused as I, because there are different comments on bitcoin investment. Any way I think that if you mean that where to invest bitcoin, so investment itself is investment and no need to invest it anywhere. If you mean where to invest the earnings of investment then you have many options in regular businesses.
just to clear you out , bitcoin itself or any other cryptos like eth , bch , xrp , etc is only a cryptocurrency . you cannot call them an investment but rather you can use them to be able to invest on other profitable activities .
@op you can invest your bitcoin on ico's becauase ico's are the most promising investments on this current year . you can earn a big bonus and perks when you invest as early as possible , plus you can sell you shares at the end of their project to earn again a huge profit .