The gearhead geniuses at the Holdur/Europcar Rental Agency in Reykjavík rented me a car without an oil cap. For the record, it is possible to drive 220+ kilometers in a VW Polo without an oil cap.
I picked up the car in the morning, got slightly turned around on the way out of Reykjavík, and headed east for a day tour of the Golden Circle - Þingvellir, Geysir, and Gullfoss. I started to suspect something amiss leaving Gullfoss late in the afternoon. In first gear with the gas floored, I was creeping around the parking lot at 10 km/hour. That on top of a weird shuddering chugging from the engine when I parked at Geysir. Mysterious signal lights were lit up on the dash, but since Holdur also neglected to include the manual with the car (why?), I wasn't sure what they were. I don't drive very often, so carspeak isn't natural for me. Also, I almost never drive a manual transmission; it wasn't inconceivable that I was doing something wrong, but as far as I know, neutral means neutral. Stopping and starting again seemed to solve the issue, which I figured out after an unplanned stop at a gas station to figure out directions, so without further stops, I made it to the Hveragerði campsite, aka home for the night. After the warden, Óli aka Þor, showed up, and gave me some info about a nearby cave I wanted to visit, I decided he was friendly enough to hit up for car advice. Fortunately it exhibited its engine shuddering bad behavior almost immediately, Óli popped the hood and…gasp!…no oil cap. One of Óli's friends showed up and also took a look. Assuring me it wasn't my problem, they whipped out their cell phones, and about four minutes and lots of Icelandic later, my problem was solved. I wasn't going anywhere for the night, but a new car would be delivered the following morning. And so it was. A brand new Suzuki Swift, oil cap included, showed up the next morning. Óli popped the hood to double check for me. And off I was to Raufarholshellir cave. Iceland really leaves it up to the tourist to take care of themselves. Raufarholshellir is a lava tube over a kilometer long. There's a sign at the start warning of its dangers, and that's it. I managed to clamber over the jumble of rocks at the entrance, past two piles of snow in caverns which roofs open to the sky, and picked my way through a forest of ice stalagmites before deciding going any further would be folly. Also, it was the start of true and utter underground darkness, and despite a headlamp, I was woefully unprepared for a caving expedition. So I just sat for a while in the cool dark, looking at upside-down icicles and listening the steady dripping of water from the roof. All the pictures I took are terrible, but maybe this one gives you the general idea.
Also, here's one from the cliff over Gullfoss, demonstrating the distinct lack of guardrails. I'm just sitting on the edge, looking down.