You can find an overview of all available land at the Land Expansion page. Right now there is missing one row, which has been added with this event, but it will be added to the page soon.
Actually, there was another row added as soon as the event was available. I play every day and as soon as I downloaded the update and got into the game the event wa live. As soon as I got into the game with the new update/event the first thing I did was check for new land and found there was a new row available on the right hand / North East side of the map. I wish they would have given us another row on the bottom as well or eve two rows on the side they did. With a an event where there are lots of things to add it would be nice to have two rows of land to add so you don' thave to spread everything out on one row.
If EA would make it possible to place all items, buildings etc. from THOH, Easter events and Clash of Clones Event in Krustyland and make it possible to create themes, then they wouldn't need to add new expansions for Springfield for every major update/event. It would also prevent a lot of lagging and players with older devices would probably still be able to play TSTO.