Learn Spanish (Latin America): Fue una lástima que no terminaran la gira. - It was a pity that they didn't finish the tour.

The phrase una lástima que expresses a judgment or emotion. Whenever the main clause expresses a past emotion, doubt, or judgment (here, fue una lástima), the verb that follows in the dependent clause must be in the imperfect subjunctive.

Why use the preterite fue instead of the imperfect era for "it was a pity"?

Both are actually correct here, but they give a slightly different feel. Using fue frames the pity as a single, completed reaction, like how the speaker felt at the exact moment they heard the tour was canceled. Using era would describe an ongoing, background feeling of pity during that time.

Could I say terminasen instead of terminaran?

Yes, you can. The imperfect subjunctive has two sets of endings: -ra and -se. They are completely interchangeable in meaning, but in Latin America, the -ra endings like terminaran are used almost exclusively in everyday speech. The -se endings sound much more literary or formal.

Can I use gira for any kind of tour, like a guided tour of a museum?