It aired in 2011 and lasted one season.
As they were finishing up the first season, they knew there was a good chance it would be cancelled (because it was a complete budget buster with on-location shooting in Australia, CGI every week and at least one big name actor I know of) but also a good chance it would be renewed (because it was the most watched new show of the season). So they tried to create a finale that would neither leave a major cliffhanger unresolved nor preclude the possibility of new stories in future seasons. It ended with the major conflict of season 1 resolved, but with new mysteries and challenges on the horizon. I was satisfied. If you like the show and end up watching to the finale, I think you will be too.