If you want to go on a quick day trip, we recommend driving the Golden Circle. In this trip you will stop at Þingvellir (where the Eurasian and North American tectonic plates meet), Geysir, and Gullfoss (waterfall).
A nice road trip around Snæfellsjökull National Park. Beautiful nature, seal beach, one of Iceland's glaciers, moss fields - a really nice day trip.
This is one of the best road trips in Iceland! You drive past waterfalls, black sand beach, glaciers, and end in a glacial lagoon. The drive there and back can be a total of up to 10 hours so it can be done in a day, but we recommend staying at a hotel on the way so you have more time to explore.