After we watched Daisy erupt, we were within the window for Castle Geyser and decided to stop by to see if anything was going on (it erupts about every 13 hours, +/- an hour). Castle is a very old geyser with a large cone formed from silica deposits (i.e. geyserite). When we arrived there was quit a bit of steam action and occasional water bursts that psyched out the waiting crowd.