The largest gathering of volcanic domes on the moon can be found in the middle of Oceanus Procellarum and close to the ring-plain Marius. Squeezed into an area of approximately 200 km in diameter the Marius Hills contains about 300 domes, half of the moon’s known population. The domes are just a few hundred meters high and thus best observed under low sun.
The sketch was made under a waxing gibbous moon, just a few days from full, and the sun angle was perfect for highlighting the many domes. Sketching them was another matter, quite cumbersome at that. Marius is the crater to the middle left in the sketch. Top right is the end of the Reiner Gamma swirl.
In 2009 the Japanese Selene mission found what might be a sky light to an underground lava tunnel in the Hills. The Marius Pit is located close to the rightmost dome in the sketch, but since it is just 65 meters in diameter it is well beyond the resolution of my scope. A fly-over movie from JAXA can be found here. Lava tunnels might be an option for a future lunar base, and apparently there is advanced plans for a private moon mission to target the Marius Pit.