The Shitennoji temple was founded in 593 by Prince Shotoku, making it one of the oldest Buddhist temples in Japan. In an industrial city it is an oasis of tranquility. Every month on the 21st there is a flea market that attracts all manner of vendors selling bric a brac, antiques, crafts, food and more. If you happen to be in Osaka when the market is on it is a great place to visit. 
