The Swallos Grotto is situated 40 km. east of the county seat of Jianshui. It is a gigantic grotto of karst formation in the ravine of the Lujiang River. During spring and summer, hundreds of thousands of swallows fly in and out of the grotto, hence the name Swallows (Yanzi) Grotto.

The grotto is divided into two sections: one to the left and the other to the right, one high and the other low, one shallow and the other deep and one dry and the other watery. The upper cave is the dry one. It is very big and bright, looking like a great hall and capable of holding a thousand people. Originally there was a three-storeyed pavilion with a giant tree growing through the roofs, called "an arrow piercing through the pavilions". It is a great pity that although the tree is still there, the pavilion is no longer to be seen. On the rock walls of the cave are engraved inscriptions composed by people of olden times, reading "A cave locks the three heavens", "A marvelous scene never to be found elsewhere in the world". etc. Climbing along stone steps on the left of the hall-like cave and going through a small hole and another stone hall, there will be seen a wooden plank road leading to another pavilion on the cliffs. The plank road is about 33 m. high, hanging over the Lujiang River, with only a wooden pillar supporting the pavilion on the protruding rock, just like a basket with eggs hanging on the cliff. It is popularly known as a "pavilion suspended in the air". It has now been reconstructed and made into a reinforced concrete "Balcony in the Air". Peeping down from the balcony will make you dizzy.

The lower cave is about 33 m. in height, with myriads of stalactites hanging down from the roof. The Lujiang River flows into the cave and becomes a subterranean river, running for 7 to 8 km. inside the cave, which is also the length of the cave. Inside the cave the roaring of the rushing river and the twittering of the swallows can be deafening. People in the old days had composed poems comparing the twittering of the swallows to the battle cries of the warriors engaged in a fierce struggle at Feishui, a famous battle field of the Eastern Jin Dynasty, and the roaring of the rushing water to the thundering of the famous surf at the mouth of Qiantang River of Hangzhou, and called this phenomenon a miracle of South Yunnan. From time immemorial Swallow Grotto has attracted numerous visitors from near and far, and people passing by this place consider it a great pleasure to pay to grotto a visit.