Cave 420 has an inverted-dipper typed ceiling and a square main hall. At the south, north and west walls is excavated a shrine respectively. The statues of bodhisattvas in this cave are cast in simple clothing with green and blue design, which forms contrast with the earth yellow tone of the wall paintings, resulting in strong decoration. The skirt of the bodhisattva, with bead design and hunting scenes in roundels, is of Persian art style. The Guanyin Bodhisattva (Bodhisattva of Mercy) holding a willow twig at the south side of the shrine at the west wall is a master piece among the contemporary statues.

The south, east and north walls depict miniature Buddhas. The caisson design at the center of the ceiling is lotus flower, while four slopes depict large-sized illustration of Lotus Sutra, which foreruns the large-sized illustrations in the Tang Dynasty and is of high artistic value.

It is one of the representative caves excavated in the early Tang period. States inside the niche has lost its original appearance due to restoration in Qing Dynasty. The south and the north walls are painted with abundant Buddhist historical stories.

The painting depicting Zhang Qian's Mission to the Western Regions on the north wall, though discrepancies exist with history, provides valuable visual material for researching the history of the Silk Road and the history of cultural exchange between China and the western world.

Each story is painted in a combined pattern, containing four or five scenes which are varied in size and interleaving. There is no demarcation between scenes or stories; instead, landscapes and architectures are painted as background, wherein human figures are placed, thus producing integrity. It is a masterpiece of the landscape and figure paintings of the Tang Dynasty.

A piece of blank is noticeable at the center of the south wall, it is vestige left over by American Landon Warner who pasted away the wall painting in 1924.

According to the Tablet Recording Li Fujun's Patronage in the anteroom, this cave was excavated by Li Dabin in the eleventh year of Dali Era (776).

On the altar at the main hall is a 15m long statue of Buddha in nirvana. Nirvana is the highest spiritual state of eternity that Sakyamuni attains at the age of 80. Behind the nirvana statue are Buddhist disciples, celestials, princes of various states, Buddha's foster mother, Bodhisattvas, total 72 statues (renovated in the Western Xia Dynasty). The west wall depicts an illustration of nirvana sutra, which is the largest in size of its kind at Mogao Grottoes.

The south niche originally contained Cintamani-Cakra Avalokitesvara statue and the north Amoghapasa Avalokitesvara, yet both statues have been damaged and respectively replaced by Buddha of the Past and Buddha of the Future cast in Qing Dynasty. The ceiling of the cave shows thousand Buddhas painted in the High Tang period, yet the color is still bright and fresh after some 1,200 odd years.

The south side of the entrance illustrates Amitayur-dhyana-sutra in large canvas and the north side Bhaisajyaguru-sutra. Architectures such as halls, turrets, yards, cloisters, waterside pavilions in those two paintings are precise in composition and fine in artistry, providing precious materials for researching the Tang Dynasty architectures. In the anteroom is extant with two warriors, two heavenly kings, and two lions cast in the Middle Tang period and renovated in the Qing Dyansty.

One of the representative caves of the Late Tang period. According to inscription in this cave, it was built during Jingfu period (892-893 A.D.) in the Tang Dynasty. The wooden roof of the anteroom is the only Tang Dynasty wooden architecture extant now at Mogao Grottoes, providing important visual material for researching the history of ancient Chinese architecture.

The main hall is square with a central altar on which are well preserved several painted statues cast in the Late Tang period, yet two statues at the south side of the altar have been damaged by a clump of fallen rock during an earthquake. The west wall illustrates a battle between Buddhist disciple Sariputra and the heretic Raudraksa, such a theme emerged during the Late Tang period and characterized the era. The whole illustration takes up more than 40 square meters and is the largest one of its kind. The textual source for this illustration is the Scripture of the Wise and the Fool. During the battle, Rardraksa successively transformed himself into mountain, buffalo, pond, poisonous dragon, yellow-headed ghost, tree etc., yet one by one was defeated by vajra warrior, lion, elephant, golden-winged bird, heavenly king, and strong wind which were transfigures of Sariputra. The illustration ends up with conversion of the heretic to Buddhism.

Artist highlighted episodes that may contribute most to optimum artistic effect. The scene of battle between wind and tree is most impressive, representing attainment of ancient artists.

This cave was excavated during the Kaiyuan Era and the Tianbao Era. It contains the second largest Buddha at Mogao Grottoes, also known as the southern giant Buddha for it is located to the south of the cave 96. The statue in this cave is 26m high, cut directly from sand-stone and then clayed, showing a sitting Maitreya Buddha. The format of this cave is like an inverted square cone with an inverted dipper shaped ceiling. From the top portions of the south and the north walls of the corridor were cut a niche respectively, with portraits of donors below. The south and the north walls in the main hall depict respectively a 15m high Bodhisattva, above are Mogao's largest flying celestials painted in Song Dynasty. A hall site of the Western Xia Dynasty exists before the cave. The 26m high Buddha has a 7m large head, though disproportionate in figure, it makes up visitor's visual gap when looking up from below, enables visitors to have a clear view of Maitreya's solemn and benevolent expression, and his sublimity as well.