A project sponsored by the Ecuadorian Tourism Board has just completed an observation deck projecting out over the crater lake at Quilotoa.
http://www.complex.com/style/2014/12/vo … in-ecuador
The pictures at the link of the deck and the lake look like it's really cool (a similar projecting deck was built a few years ago at Grand Canyon).
Google maps says that Quilotoa is about 2.5 hours south of Quito, and about a hour west of Latacunga.