Morning Glory Pool
Morning Glory pool is named for its shape, which bears an obvious resemblance to a morning glory flower bloom. It is a rather large pool, and has always been a favorite of tourists. Too much of a favorite, unfortunately -- its behavior has been negatively impacted by early visitors throwing pennies and other foreign objects into it, which can ruin a hot spring or geyser. Fortunately, most Yellowstone visitors now are a bit more enlightened (though not all, sadly.)
You can see Morning Glory's runoff channel near the top left.