When you break down travel into its essential elements, you start to see patterns emerge.
As I jaunted about town (town currently being Singapore) today by taxi, bumboat, escalator, staircase and metro, enjoying restaurant, museum, statue, skyscraper and crowds, I found myself musing on a general theory of tourism.
The way I see it, all tourism can be reduced to six categories (view handy diagram here).

On the other hand, if you decided on your first day not to do it, but it’s now your last day and you haven’t spent your budget, you might look at the money you have and compare it to the cost and decide that it’s now worth it.