Pathum Wan District saw increasing development throughout the 20th century, especially since the 1970s when the area along Rama I and Phloenchit roads became developed as a major shopping and commercial district. The Erawan Hotel opened on Ratchaprasong Intersection in 1956, and the Thai Daimaru department store, famous for introducing air conditioning and the escalator, opened on the opposite corner in 1964. Siam Square was developed as a low-rise retail area by Chulalongkorn University the same year, and the Siam Inter-Continental Hotel opened opposite it in 1966. Rajadamri Arcade—a modern, enclosed shopping mall—opened at Ratchaprasong in 1972, and Siam Center (next to the Inter-Continental) followed the next year. Gradually, Siam and Ratchaprasong supplanted the Wang Burapha area as Bangkok's centre of urban retail and youth culture. With the opening of the BTS Skytrain in 1999, the location of its central interchange at Siam station helped cement the neighbourhood's prominence as Bangkok's modern-day city centre. The area's prominence led to its occupation by anti-government protesters in 2010, which ended in a violent military crackdown.