What does "He explores the city on foot." mean in English for Spanish?

In English for Spanish, "He explores the city on foot." means:

Él explora la ciudad a pie.

Listen to "He explores the city on foot.": (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 4, Level 3, Scene 4