everyday Chinese 每日汉语口语 - 天涯原咫尺，到处可逢君

天涯原咫尺，到处可逢君。World is but a little place, after all.
Explanation: It is used when a person meets someone he knows or is in someway connected with him in a place wher he would never have expected to do so.
Example: (在火车上，你突然遇到一个同公司但不同部门的同事，你说) 怎么你也出差去深圳吗？真是天涯原咫尺，到处可逢君哪。