Word for a public place where people frequently come in contact with one another

Solution 1:

The words "busy" or "bustling" fill in the blank in your example sentence, or they could be used in combination with some form of "public place" to fit your need.

busy (adj.) full of or characterized by activity: a busy life.

bustling (adj.) to abound or teem with something; display an abundance of something; teem (often followed by with ): The office bustled with people and activity.

Solution 2:

... somewhere public.

Or

... somewhere heavily trafficked.

Solution 3:

It's a little bit literary, but frequented or well frequented.

In less formal language I would say somewhere where people go.

Solution 4:

In Ancient Greece, it was the agora. It is difficult to find a modern english equivalent. A few hundred years ago, it was the public square or the market place. Last century, it might have been called the "High Street". I fear that in 2012 it may "the mall".