There are astounding views of glaciers nearly everywhere in Iceland. Glaciers cover 11% of the landmass (most of the interior) of Iceland, most of them over volcanoes (which can lead to some serious flooding problems when the volcanoes get burpy and heat up the ice over their craters).
According to Wikipedia, the 13 larges glaciers cover an area over 11,000 square kilometers. Vatnajökull is the largest, with 8300 of those square kilometers. It lies in the southeast and a drive along Route 1 can view the many glacier tongues coming down the mountain. The spill of compressed snow and ice reach down almost every canyon, and one of the most popular tourist sites in the south is the glacial lagoon of Jokullsarlon — icebergs calving off the glacier flow out to the sea.
There are dozens of glaciers visible from the main road, and it is tempting to go traipsing off to hike on them, or see them up close. Don’t. Glaciers are dangerous — do not, under any circumstances, climb onto a glacier without expert guidance. They can be riddled with fissures and crevasses and it would be trivially easy to fall in. There are news reports every year of stupid visitors walking out on the ice and having to be rescued. Most of them aren’t injured, luckily, but it does happen.
If you want to hike out on the glaciers, there are plenty of tour companies with expert guides and equipment, or super-jeeps, who can take you out on the ice. Try: