The Great Bell Temple is located on the western outskirts of Beijing. It houses the largest bell in China. The bell was also named Yong'le Bell after Ming Emperor Yongle who ordered it be cast about 600 years ago.

According to a recent test by the Chinese Academy of Sciences, its loud and clear sound reaches up to 120 decibels and can be heard 50 kilometres away in the depth of night.

Music experts of the Chinese Acoustics Institute have found its tone pure, deep and melodious with a sprightly rhythm. Its frequency ranges from 22 to 800 hertz.

The bell is known as China's "king of Bells," which is 6.75 metres high, 3.3 metres in diameter and 46.5 tons in weight.

Specialists from the Beijing Foundry Society and the Beijing Metallurgical Engineering Institute studied the bell and described the technique as "ground pit casting with a pottery clay coated mold."

According to the specialists, the clay mold had been put in a pit in the ground and the molten metal poured in at one stretch through two holes on the top of the mold. An ultrasonic examination of it found very few sandholes. To achieve such a precise calculation, accurate timing and huge heating system were needed. The experts also found the bell's metal a perfect bronze alloy - 80.54 per cent copper, 16.4 per cent tin and 1.12 per cent lead. Even when struck hard, it produces a fine sound.

But the most difficult part of the casting was the Buddhist sutras inscribed over the entire surface of the bell both inside and out. There are altogether 227,000 Chinese characters inscribed on it.

The third Ming Emperor Yongle took power in 1403 after a coup known in Chinese history as the Jingnan (Pacification) Coup. Legend has it that, feeling guilty, he tried to atone for his misdeeds by having the great bell cast with 17 sutras. He hoped to "divert public indignation by striking the bell," according to an "Ode to the Great Bell" inscribed on the tablet erected during the reign of Qing Emperor Daoguang. The tablet still stands by the side of the bell.

The bell was originally kept in the Imperial Longevity Temple. Shipping the bell from the foundry to the temple was a big problem, since there was no vehicle or machine that could handle it. A ditch was dug along the way, and water was fetched from newly-sunk wells to make an ice route in winter. Placed on a huge sleigh, the giant bell was hauled to its destination by oxen. In 1733 the bell was moved form the Imperial Longevity Temple to the present site.

In addition to the Yongle Bell, 31 other bronze bells from the Song, Yuan, Ming and Qing dynasties are also on display outside the temple.

At present, the museum is devoted to ancient bells. It is China's first bell museum set up in 1985. The museum features a display illustrating the evolution of Chinese bells and the history of Chinese metallurgy. The bells on show have been collected from all over China. Some of the bells were moved here form the temples in Beijing.

Most of the bells are made of bronze, and the oldest was cast 700 years ago. The most famous of all is the great bell which gave the temple its name. The exhibition was opened in 1986.