Final answer:
In 'The Phantom Tollbooth,' Milo first sees a gate as he approaches Dictionopolis, signifying the start of his adventure into the realm of language and words.
Step-by-step explanation:
In the book "Phantom Tollbooth," the first thing that Milo sees as he approaches Dictionopolis is a gate. This gate is likely analogous to the gates found in intricate city designs, such as the Gate of Supreme Harmony described in the Forbidden City plan. Just as people might meditate as they approach the grand entrances of old cities surrounded by towers, Milo would be filled with anticipation and curiosity about the new world he is entering.