The country code for all of Costa Rica is 506.
If you are calling internationally, you dial the international access code, which is 011, then the country code which is 506, then the 8 digit phone number.
If you are in-country, you just dial the 8 digit phone number from any phone.
Why 8 digits?
Costa Rica has the regulation 7-digit phone number with a 1-digit area code. We have only two "area codes": 8 for mobile phone numbers and 2 for land lines. So all 8-digit phone numbers start with either an 8 or a 2.
