Iceland possesses an amazing array of diverse ecosystems. 10% is covered by lava; 11% is covered by ice caps and 75% of the country is without vegetation. Despite the extreme harshness of much of this land, where there is vegetation it can be as lush as Ireland, complete with numerous rainbows.
As you drive the Ring Road, roughly an 8-day trip, you are constantly surprised. You might see huge glaciers looking like they will soon engulf the farms which look tiny against their flank. You will discover that the largest waterfalls in Europe are found here. Some are vast abysses unfettered by fencing and unspoiled by kiosks selling souvenirs. You may be the only person or just have a handful of others reveling in this display of Nature's raw power.
In the South East you can take a boat ride in the iceberg-filled lake of Jokulsarlon. The opening scene of a James Bond movie, A View to A Kill, Was filmed here. The best time weather wise to visit is during the summer months when in addition to warmer weather, the sun never really sets.