What does "playing in a hole" commonly used in ancient poetry mean? What's the allusion?

Browse the caves. The ancients said that playing in the caves mostly refers to viewing the stone carvings on the cave walls and leaving impromptu works, including aphorisms, poems, calligraphy, etc.

For example: In April 1860, Shi Dakai "inspected the wilderness with all the officials" and "Denzi Ancient Cave", and read the wall poem written by Liu Yunqing from Hunan in the Qing Dynasty, "A strange land comes from the sky wall, climbing into the sky." The rain is coming from afar, and the water is howling in the wind. The ancient Buddha describes it as strange, and the strange man looks majestic. Looking back, the sword flies away to make a rainbow." Later, he was so heroic that he wrote a poem with a wave of brushstrokes: Stand up to climb the mountains, raise your eyes to illuminate the distant sky; Destroy the Buddha and worship the emperor of heaven, immigrate to the retro style; When approaching the army, you will be praised as a brave general, and you will play in the cave to admire the heroic poets;

< p>The sword energy rushes into the stars, and the literary light shoots up the sun and the rainbow.

The ten civil and military officials who accompanied the tour also wrote a poem each and engraved it on the wall afterwards. The poem is 108 cm high and 145 cm wide. The stone surface is smooth, the edges are neat, and there are no patterns. The calligraphy is all in regular script, and the characters are 1.5 cm long. This is the only existing stone carving of poetry and prose of the Taiping Heavenly Kingdom in the country.