You can roll it over to a bank of your choice such as maybe etrade, fidelity, charles schwab, etc. You can leave it and let it continue to grow. Do you plan to get another job? It really just depends what you want to do with the money and if you would rather roll it over for example into an investment account and buy your own stocks/mutual funds or if you'd rather just leave it in a retirement target fund which basically takes care of that stuff for you.
Some things to consider are the fees you are currently paying, vs what else is available. The value of your account could get you bonuses if you roll it over to another bank, but usually have to have above 10 or 20k to roll over for bonuses.
