The Solar Empire campaign is full of interesting things to explore. It probably has the most secrets, too. For example, the "Showdown at Big Honshu." Look at the map. You can swim almost anywhere, even the recon's path to the silos. Here's the coolest one. Go to the recon helipad location. (alone or with squad) Destroy the battalion garrisoned there along with their reinforcements. Check your map. Just outside the path out of the base, there's a lake with a slightly visible rope bridge. It looks like it's out of bounds, but it's not. Go to it. As you cross the bridge, you notice a large Anglo tent. Get closer and you see it's an abandoned camp! Walk to the shore's edge and you will find an huge destroyed Solar battleship, and a beautiful view of the volcanoes! You can also reach the very end of where Koji stopped designing. Have fun exploring!