Climbing of course!!
I wish I had a better picture (I think there are some on the camera now) of their climbing skills. This is more an example of play than climbing. They climb up the side of the couch, over the recliner, onto tables and into cars. They even scale brick patio walls. This is especially terrifying for me, but they have not fallen yet. I'll just keep holding my breath and having small heart attacks while they discover their world how they see fit.