This is where Carter and Flora live and are employed. Any time that Carter is inside the dig site, you can talk to him, and he will allow you to dig. You can dig until 5PM each day, at which point Carter will stop you and ask if he can look at what you've dug up.
The player is allowed to keep everything that he/she has dug up, with the exception of tablets which Carter will keep. The dig site will expand each year, assuming that the player has found a tablet in each year.