3 day itinerary questions

On Day 3, you need to be at the airport by 11:00, and you'll need to leave Reykjavik by 10:00 to get to the airport and return the car. Not much time to do much in Reykjavik that morning.

On day 2, maybe look at a day jeep tour of Þórsmörk from Midgard Adventures? (We found them originally thru RS.) It would allow you to experience something special on your backtracking to Reykjavik. They have a restaurant there where you could grab a bite after the tour, which might be more time efficient too. Just a thought.

The way you have it set up, you do not have time for Snaefellsness unfortunately. Day one looks good. On day 2 you could go to Westmann Islands for the day, or if you can get a room, stay the night. If your flight is ack to the US, you need the full 3 hours at the airport, plus time to return the car. So plan to be there no later than 11am.

As for hot springs, Sky Lagoon is right in Reykjavik, although on the outskirts so not really walkable. That would be good for arrival day. Otherwise in the GC you have several options. Secret Lagoon and Fontana are both great, just very different from each other. Secret has pool noodles, which I like because I am short and these keep me up;) Fontana has the cold plunge right now there in the lake, or you can do the bucket drop cold plunge right there on land. There is a new hot spring opening up next month, Laugaras, so check that out. They are late on opening due to construction delays, but keep an eye on it. There are also rustic hot springs that are great, such as Hraunalaug. I have been to all of these, several times each, and you can't go wrong with any of them. Don't forget the local pools as well.

Thanks! We will check out those hot springs.

One more question about local pools. Are there any along the GC route?

In the heart of the Golden Circle, no, but Selfoss does have a pool. There is also Hraunalaug in the GC which is a very rustic hot spring. It is very small and they limit the number of people due to that, but it is really enjoyable so I would aim for that.

Hello

Your plan sounds interesting. How are you are combining the Golden Circle route and the Southern route/detour? What route will you take? Can you elaborate?

We are also visiting Iceland for a brief stop over and I thought we would have to choose either a Golden Circle day or a South Coast day because I’m not sure we would have time for both. We land after a long overnight flight on a Thursday morning, pick up a car and fly out again on Sunday morning. We will have a jet lagged partial first day and 2 full days with accommodation in Reykjavik.

We added the stop over on our way back home so our flight to Reyjavik is only 4 hours long. We get to Iceland late afternoon and stay there that evening. We plan to leave early the next day for the GC and detour to Vik. We have reservations to stay in Vik that night. If all goes well, we will get back on the GC the next day head back to Reyjavik. We will stay there and leave the next day. We watched Rick Steves take this detour in his Iceland video and thought we would give it a try. I thought our flight was a 2 pm but we actually leave at 4 pm so we will have a little time to explore Reyjavik before we leave.

Google says you can do it this way:

Here's a breakdown of the detour and how to incorporate it into a Golden Circle itinerary:
Golden Circle Route (General)
Reykjavik: Start your journey from Reykjavik.
Thingvellir National Park: A historical and geological site where the North American and Eurasian tectonic plates meet.
Geysir Geothermal Area: Witness Strokkur, a geyser that erupts every few minutes.
Gullfoss Waterfall: A powerful two-tiered waterfall, considered one of Iceland's most beautiful.
Return to Reykjavik or Continue to Vik: This is where you'd make the decision to either head back to Reykjavik (completing the loop) or continue your journey to Vik.
Detour to Vik
Leave the Golden Circle: From the Geysir area or Gullfoss, head south on Route 37 (also known as the Golden Circle's southern leg).
Continue on Route 30 and Route 1: Follow Route 30 south, which will eventually merge with Route 1 (the Ring Road).
Follow Route 1 South: Continue on Route 1 (the Ring Road) towards Vik.
Arrive in Vik: Vik is located on the south coast, accessible via Route 1.
Driving Time and Distance
The Golden Circle itself is about a 230-kilometer loop.
The drive from the Golden Circle to Vik is approximately 150 kilometers and takes about 2-2.5 hours, depending on road conditions and traffic.

Hope this helps.