Airport trips I like the most for the same reason, but they never take 9+ days. Tynan made a good point.
"Airport trips"? Can you elaborate?
When I was a student and had lots of free-time in the summer. I did some trips where I intentionally spent long hours on airports. Taking advantage of the many low-cost airlines in Europe, once I managed to buy a whole Budapest-London-Cork, Dublin-Barcelona, Barcelona-Budapest trip for $120. That made a trip with 5 flights, 8 different airports in 7 days and 3 cities where I actually stayed over.
I find airports very neutral in-between spaces and thus perfect for concentration and work.