What does "They are walking through the Boston Common." mean in English for Spanish?

In English for Spanish, "They are walking through the Boston Common." means:

Ellos están caminando por el Boston Common.

Listen to "They are walking through the Boston Common.": (If you have an HTML5 enabled browser, you can listen to the native audio below)

This is a phrase that is used in the GamesForLanguage English for Spanish Language Game in the following scenes:

• English for Spanish 3, Level 2, Scene 7