File:King crater pool hrp154.jpg

English: The pool north of King crater, now known as King Y crater. This is Figure 155 of Apollo Over the Moon (NASA SP-362, 1978), which has the following caption:
The Apollo 16 astronauts captured this spectacular view of the large dark "pool" on the north flank of the crater King as they approached from the east. The pool (also known as a lake, pond, or playa) is in an old crater swamped by King ejecta. The maximum width of the pool is about 21 km. The peculiar dark material that forms the large pool and also coats adjacent hills was first discovered on Apollo 10, and was later seen again from Apollo 14. The most exciting part of the discovery had to wait until the mapping and panoramic cameras of Apollo 16 showed that this material contains some of the freshest and most spectacular flow structures on the Moon. These structures, some of which are seen in the following figures, show that the material behaved like lava. The material is very similar in appearance to that filling parts of the floor of King. -K.A.H.
This photo is used in Figure 29-88 of the Apollo 16 Preliminary Science Report (NASA SP-315), which has the following caption:
Oblique view, looking westward, of the northern segment of King Crater and the dark, pool-shaped deposit on its rim. The obliquity of the view clearly shows the various levels from which the dark material flowed to fill the floor of an old depression.