Where is the best place i can invest some money? I dont want high returns (high risk) i just a really safe long term (low risk) deal for my retirement fund.

#1. Under your mattress is stupid. No interest whatsoever, and if your home is broken into, you're screwed.
#2. Burying is even worse. Unless it's in a 100% airtight vaccuum sealed leakproof container, your money is going to decompose and be completely worthless by the time you're ready to retire (assuming it's going to be a while) And, once again, no interest earned.
#3. C/Ds are Certificates of Deposit. You put the money in for a predetermined amount of time without withdrawing it and when it has matured you can take it out or put it into a new C/D. You're interest rate is set for the entire time. Some banks offer Callable C/Ds which means you have a slightly higher interest rate at the time of deposit for a set locked in period. After the locked period expires, you must be prepared to leave the money in the C/D for the remainder of the agreed upon time. If, however, interest rates have plummeted well below your interest rate, the bank has the option to "call" the C/D, allowing you to take the money out without penalty or roll it into a new C/D at a presumably lower rate or leave it in the current C/D at a new lower rate. The downfall is, if rates skyrocket, the bank won't call the C/D, and it has to stay there unless you want to pay early withdrawal fees.
#4. Depending on your age, your options are wide open. If you are in your twenties, get into your company's 401(k) if they offer one. Short term, it sucks, but by the time you retire, the economy will have turned around and you'll have a nice retirement nest egg. If you're older, I'd recommend C/Ds or a money market savings account. They're both better interest than a basic savings or your mattress, and there is no risk involved.

Under your mattress

You should look in to CDs...they are not the highest, but can be relatively 'safe'....You should also 'ladder' them; say you have $5,000 to invest; you'd take out one CD for 6 months, with $1,000, then another for 12 months, another thousand, then 24 months, then, then 36 months, then 48 months...when the first one comes due, move it in to the longest-term CD; next one comes due, do the same; this way you still have access to your money if you need it...& you'll find that the longer terms have a slightly higher return, as your money's kept in the CD longer...I use Ameriprise; with their CDs, you can withdraw all of the interest and up to 10% of the total, with no penalties!! BUT you still have to pay tax on it, of course......hope this helps!! let me know if I can help any further!!

The stock market can be very low risk if you invest correctly, Specifically, investing in Blue Chip stocks can provide a consistent rate of return very safely. Most Blue Chip stocks pay a quarterly dividend and if your stock is enrolled in a Dividend Reinvestment Plan (DRIP) those dividends are used to purchase more shares of that stock.

enrolling in a DRIP:
http://www.ehow.com/how_5289084_enroll-dividend-reinvestment-plan.html

using Dividend Stocks for retirement:
http://www.ehow.com/how_5335423_use-dividend-stocks-retirement-planning.html

Over time, dividend stocks can create a nice nest egg for retirement.

The stock market can be very low risk if you invest correctly, Specifically, investing in Blue Chip stocks can provide a consistent rate of return very safely. Most Blue Chip stocks pay a quarterly dividend and if your stock is enrolled in a Dividend Reinvestment Plan (DRIP) those dividends are used to purchase more shares of that stock.

enrolling in a DRIP:
http://www.ehow.com/how_5289084_enroll-dividend-reinvestment-plan.html

using Dividend Stocks for retirement:
http://www.ehow.com/how_5335423_use-dividend-stocks-retirement-planning.html

Over time, dividend stocks can create a nice nest egg for retirement.