"What was most amazing was to hear the rumbling noise," said an exhilarated Aslaug Gudrunardottir, who said she stood only a few meters (yards) from melting lava.
"It was like standing on top of an ancient monster down in the ground. It is a sound that is impossible to imagine," she told AFP back down at the foot of the mountain.
The Fimmvorduhals volcano in the middle of the Eyjafjallajokull glacier erupted on March 21, the country's first such volcanic explosion since 2004 and the first in the Eyjafjallajokull area since 1823.
It forced some 600 people to briefly evacuate their homes in this remote, lightly populated area 125 kilometres (75 miles) east of the capital Reykjavik. But it has since turned into a boon for a local hotel and a few bus firms offering twilight tours -- and a headache for police and rescue workers.
News from geologists this weekend that the eruption may be peaking and could soon "diminish dramatically" sent thousands of visitors rushing to catch a rare glimpse of a real live volcano and the majestic "lava falls", with red-hot burning lava cascading hundreds of metres down a gorge.
Cars stood bumper to bumper in Fljotshlid, across from the glacier, as hundreds of people made their way up to the smouldering peak by foot, snowmobile, helicopter, even motorcycle. A popular hiking trail, it was re-opened last week though police warned anyone taking it they did so at their own risk.
"People do not understand the danger. That is what our rescuers have been saying all weekend," moaned Bryndis Harardottir of the Ice-Star rescue service. "It is an eruption, which is dangerous, even if it is majestic and beautiful."
A number of tourists had wandered into areas that could easily have been cut off by the lava flow, she told AFP.
"People have been going too close to the crater and putting themselves in danger as there can be explosions at any time. They forget that this is a volcano," she said.
Even without the eruption, trekking the 1,100 metres (3,600 feet) to the top of Fimmvorduhals is not child's play. This weekend, the wind chill alone sent temperatures down to minus 30 degrees C (minus 22 degrees F).
"People have to be in good shape and dressed for the conditions," which was not always the case this weekend, Harardottir said. Rescue workers brought down several ill-equipped tourists, including one "dressed in jeans and a leather jacket showing signs of hypothermia."
Geologists warned that the Fimmvorduhals volcano could set off the nearby and much larger Katla volcano, but so far it has shown no signs of activity.
For some, Fimmvorduhals was not their first volcano.
"This is my fourth eruption," filmmaker Olafur Rognvaldsson told AFP, staring up at the orange-red glowing mountaintop from a safe distance.
"I got very close to Krafla last time it erupted," he said referring to a volcano in northeast Iceland that exploded in 1984. "We walked up there with a group of tourists on the first day of the eruption, right up to the crater."
"It was a great tour, but in hindsight it wasn't a very smart thing to do," he chuckled.
Despite hindsight, Rognvaldsson still wanted to take a helicopter to get a closer look at the fiery Fimmvorduhals, then get out to explore the ridge of the crater.
"It is a very beautiful sight from a distance, but it is totally different to experience it from up close," he said.