Once you cross the bridge to Shamian Island, you feel transported to a different country. The architecture is European and the shop owners speak English. Chinese and foreigners stroll through the quiet streets and lush parks. The most well known Catholic church is on the island, and it's a popular locale for wedding photo shoots.
Shamian Island has a long history of trade and war. After the second Opium War in the mid-19th century, Britain and France took control of the island, barring the local Chinese from it except for menial jobs (they were kicked out each night). Now, it's a place of tourism, foreign consulates, and a smattering of hotels.
You can spend all day on the island: wandering, relaxing, eating, and drinking. There's plenty to do, or it's a good place to do nothing and escape the busy city life.