According to the [Wikipedia page for "Symphony"][1], during the 17th century, the symphony had a fairly set structure:

> The four-movement form that emerged from this evolution was as
> follows:
> 
> 1. an opening sonata or allegro
> 2. a slow movement, such as adagio
> 3. a minuet or scherzo with trio
> 4. an allegro, rondo, or sonata

While it may not completely fit the above structure, Mahler's *Symphony No. 3* often runs 90 to 100 minutes. So "symphony" is a candidate answer. Operas often run longer than 90 to 100 minutes, but might not have a clearly set structure.

  [1]: https://en.wikipedia.org/wiki/Symphony