So Many Choices
Getting there is half the fun! So it's been said about adventure travel. And circuling the globe can certainly be an adventure.
Flying is Faster
"Round-the-World" fares often include stops in specific cities on each continent, but may be limited to cities along a specific airline's route system.
Airline "alliances" include the opportunity to circle the globe using a combination of airlines serving almost every commercial airport on the planet. The airfare will change as you add cities to your trip, but you'll find yourself seeing more of the globe.
Crossing the Ocean by Plane
It's often the only way across the ocean. Between New York City and Southampton/London may be the only exception, where a weekly sailing is offered on a luxury cruise ship.
From London eastbound around the world there are some exciting options. Eurostar from London to Paris is the start of the journey.
Taking the Train Across the Globe
From Paris onward to Brussels, Frankfurt and Moscow, you can reach the far expanse of Russia, with connections to Mongolia, Shanghai, even Ho Chi Minh and onward to Southeast Asia.