It's not easy in the tropical midday sun to capture the whole of Lake Atitlan in one picture, but here's an attempt, two photos combined, taken from the top of the San Pedro volcano. On this page from Google Maps you can see the point as the peak almost at the left end of the lake.

The view reminds me of several Norwegian lookout points to similar lakes. From this point down to the lake there are about 1200 vertical meters.