1 {scene: in a plane}
1 Prof. Jones: We could see five of the Seven Wonders of the World on this trip!
2 Prof. Jones: We’ve seen the Great Pyramid. The Lighthouse of Alexandria is next.
3 Prof. Jones: Then on the way to Çanakkale we pass Rhodes, Halicarnassus, and Ephesus, sites of the Colossus, the Mausoleum, and the Temple of Artemis!
4 Monty: Did we go back 1700 years in time, or was it just your brain?

The Seven Wonders of the World is a group of ancient structures based on lists by various Ancient Greek writers, said to epitomise the marvels of the world as known to Ancient Greece. Early lists varied slightly in which structures they mentioned, and the present list crystallised during the Renaissance.

Texts attributed to Antipater of Sidon and Philo of Byzantium, who both lived around the 3rd/2nd century BC, list the following structures:

• The Great Pyramid of Giza.
• The Walls of Babylon.
• The Hanging Gardens of Babylon.
• The Temple of Artemis at Ephesus.
• The Statue of Zeus at Olympia.
• The Mausoleum at Halicarnassus.
• The Colossus of Rhodes.

Later lists, and the one considered canonical today, removed the Walls of Babylon and replaced them with the Lighthouse of Alexandria. There is solid archaeological evidence that all of these structures existed - except for the Hanging Gardens. No existing Babylonian texts make any mention of such a structure, and no remains of it have ever been identified. It's possible that the Gardens existed and were destroyed without trace; or that Greek accounts erroneously refer to some other actual structure elsewhere; or that the Gardens were entirely mythical.

The Great Pyramid still exists, but all the other structures were destroyed by various means from antiquity (Colossus) to the 15th century (Mausoleum and Lighthouse). The Colossus collapsed in the Rhodes earthquake of 226 BC, but its ruins were visible in situ until 653, when Arab invaders carted away the remains and destroyed them, probably melting down all of the bronze. The Temple of Artemis existed until 268, when it was destroyed by raiding Goths, although it remains unclear how thorough the destruction was, and what remained to be seen as it decayed over the next few hundred years. The other Wonders (besides the Gardens, which may not even have existed) could be viewed until at least the 5th century, when the Statue of Zeus suffered its destruction. So, assuming you'd be satisfied seeing the collapsed Colossus, you could see all of the five Wonders mentioned by Professor Jones here any time before 268 (and after 280 BC, when the Lighthouse was constructed), around 1700 years before this comic is set.

But he's correct in that the five he mentioned could be seen in one simple trip. From Giza to Ephesus, you pass Alexandria, Rhodes, and Halicarnassus, in almost a straight line, as you can see from this map. (Babylon is far off the right of the map.)