is a bubbling, sinter-lined pool on the west side of Castle Geyser, just a few feet from the path - the cut-off trail linking the east and west sections of the main Upper Geyser Basin Loop. It is continuously active, sending water up to six feet high, though usually a few inches. Surrounding the spring is a raised rim of undulating sinter; the very shallow run-off pool beyond is colored dark brown by algae, the dark hue reflecting the relatively low temperature of the overflow water.
From here, the last thermal feature on the tour, the Old Faithful parking area is 0.7 miles south.
Back to map of the Upper Geyser Basin