Visiting the Sphinx observatory

Grindlewald would be closest if you'll be driving into the Jungfrau region. SwissRail is a great way to access the area, and would enable you to consider the car-free villages of Wengen and Murren. Wengen is probably closest to the rail connection up to Jungfraujoch/Sphinx, but all 3 are close. (Actually, Kleine Scheidegg -- with a single hotel -- is the closest.) My choice would be a rail pass to cover Zurich/Jungfrau; then either continue to travel by rail or, if you prefer driving, pick up a rental in Interlaken for the German leg.

What are your plans after leaving Hausach? Going back to Zurich to fly home, or going somewhere else and fly home from there? Since you want to go to the Jungfraujoch, your best option would be to buy Half fare Cards on arrival, then travel right from the airport on the train to Wengen and stay there, The Half Fare Card actually is cheaper than a Swiss Travel Pass because it covers 50% of the ride up to the Jungfraujoch, whereas the Swiss Travel Pass only covers 25% of the cost.

Much of what you want to do with a car rental is where you are going to turn it in.

From Hausach we are continuing on to Wurzburg to see my husbands family and staying with them for a few days before making our way back to the Bavarian area for a while then out of Munich.

You're aware you can't spend the night in the Sphynx, right? The closest hotels would be in Kleine Scheidegg. I love spending time in Switzerland, but I really wouldn't want to stay there. The most convenient place to stay would probably be Wengen or Grindelwald. Of course Lauterbrunnen is also a viable option.

You don't want to rent a car in Switzerland and turn it in in Germany. They would have to transport it back to Switzerland before they could rent it again. You would be liable for those costs as well as the days of lost rental income before that happens. So they will tack on a fee to cover those costs and then some. Plus, a German car will have the required umweltplakette to drive inside big cities with pollution controls.

Go to the Berner Oberland by train, then return by train to Freiburg, Germany and rent a car there and return it at Munich airport. The Half Fare cards will cover you to Basel, and Basel to Freiburg is a cheap ticket.

At Zurich airport, after getting through immigration and claiming your luggage and walking out the green door, you can be on a train to the Berner Oberland within 30 minutes. The train station is in the basement of the parking/shopping structure across the street from the airport exit door. Or take the overhead pedestrian bridge. Trains are 3 times per hour and it takes 3 hours to get to Wengen, the most convenient and pleasant place to stay for a visit to the Jungfraujoch.

Are you speaking of Hausach in the Black Forest? If so, it is part of the KONUS network which offers free train and bus transportation to visitors staying in the town, valid all over the Black Forest and down to the Swiss border. So renting a car and having free trains (2nd class, not ICE) gives you double transportation. Train to Hausach from Interlaken is not difficult.

What reasons do you think you need a car?

Are you planning 3 trips up the Jungfrau for 3 visits to the observatory? Or do you have an invitation to a special astronomer event there?

3 people going to the observatory no invitation by anyone ( I wish :) ). We want the car for the flexibility and once we see his family they wont have room in their car for us. Sometimes when traveling by train is not familiar for you, especially with connections in another country. You get what is, so that's why we want the rental.

That is why I would wait until you get to Germany and rent there.

I appreciate that using a train can be intimidating if you are not used to it. But if you can fly you can take a train - it is 100 times easier.

From Zürich to Interlaken Ost is easy. There are two good routes, one very scenic and a little slower, via a change at Luzern (Lucerne for Americans) over the mountains with floor to ceiling windows - and ride the send train to its last stop, and then up the hill. The other, via a change at Bern, has two storey double decker trains with normal but very large windows and even a playground for the kids, but it goes the flat way. You ride the second train there to the end of the line and then up.

From Interlaken Ost and then up the Jungfrau is all very clearly spelled out - with all the possible choices and walking paths and loads of things to do - in Rick Steves' exceptionally helpful guidebook.

If you want to consider the train ride to Hausach (be sure to see the model railway there, it is truly spectacular) then it is only one German ICE train (as fancy as they come, even in second class - pictures and video at Seat61) from Interlaken Ost to Offenburg which is the second stop in Germany, and then the little local train to Hausach from there. You can have a quick connection in Offenburg of 6 minutes, easily done by most people or just wait 25 minutes longer for the next one. If you plan ahead it can be quite cheap, and there is no airport security or baggage check or baggage carousel at the other end because you have your luggage right with you.