According to an old Thai tradition, a city pillar has to be built upon the establishment of a new city, to provide a home for guardian spirits. King Rama I had the Bangkok city pillar erected near Wat Phra Kaeo on April 21, 1782, an astrologically determined date for the auspicious founding of Bangkok. The city pillar includes the city's horoscope inside. Every town in Thailand has a similar city pillar shrine, so there are thousands of these all across the country. The original pillar was carved out of cassia wood, measuring 75 cm thick and 27 cm high. In the reign of King Rama IV, the old dilapidated pillar was replaced by a new one that measures 270 cm in height with a wide base of 175 cm. At that time it was placed in the prang-shaped shrine as seen today. Thonburi was merged into Bangkok in 1972, and its city pillar has been incorporated in the shrine. Hundreds of locals pray and place flowers here every day, as they believe the shrine has the power to bring good luck. Traditional dance ceremonies are often held, paid by wealthy families that saw their wishes granted.