Paris for one day

You'll need an advanced ticket to go to the top of the E.T. You may have to wait in line 1-2 hours if you show up without one. It doesn't sound like your schedule will allow for the wasting of 1-2 hours.

We will be buying the advanced tickets in a day or two. I might cut the Arch out. As I want to have a little time to relax. Enjoy the food and wine. Ill be back for a longer trip in the future. Just can't pass it up since we will be in London for 11 days.

Good for you! Get the ET tickets as soon as they go on sale for your date because they sell out quick. If the top level is unavailable, I thought the middle level was still pretty darn high.

Do go to the top of Arc de triumphe. In my opinion is has one of the best views of Paris because you see the round about, the broad avenues, and the Eiffel Tower from a totally new perspective. Would do that rather than going to top of the Eiffel Tower. But that's just me.

It's not just you, TC. I know I sound like a broken record if one were to read my past comments, but compared to the Eiffel Tower, better views are available for little or no cost (or wait) at the top of l'Arc de Triomphe, from the Trocadero, and from the terrace at the Galeries Lafayette department store.

If you would like a great view of Paris that includes the Eiffel Tower, go to the top of the Montparnasse Tower. There is an elevator that goes to the top and it is less crowded to than going up the Eiffel......
here is a link with some info.
Montparnasse Tower

Take the least amount of photo equipment that you can. People will jostle you because they just want to rush through the place - there are a lot of little kids here. You won't have a lot of time to set up a tripod, or even change lenses for example.
It's damp and chilly down there, which might have an effect on your lenses.

Thank you everybody. Main concern was the catacombs since I want to see that the most. I downloaded a camera app for my phone, though allow me to take better pictures in the dark caves. Ill still take my big camera for other things outside. On the camera stuff...since I saw that you can take backpacks, can I have a tripod with me, just not set it up?

Oh...how are the taxis over there?

Yes for the tripod - don't set it up in the Catacombes.
You can hail regular taxis on any busy intersection. Just look for the green light on top.
There is a lot of road work in Paris, so I would take time into consideration.
Use Google Maps to estimate travel time.

I took my catacombs photos with a little point and shoot and it worked out pretty well.
https://janettravels.wordpress.com/2013/01/12/catacombs-a-creepy-paris-stroll/

You don't want across town from the train station for your last activity and the Eiffel Tower is not something to have a tight schedule with. If you are going up, it needs to be long before a need to leave for the train. You have to wait for the elevator to the top and again to floor two and then to the base. It is not something that lends itself to speedy. I'd organize the day so you finish with something closer to the train station.

Instead of a taxi I would nevertheless try to use the metro or think about combining it as with a taxi (if budget is no issue) you will see more of the city, but also be aware can lose valuable time due to busy traffic. The metro is most of the time much quicker.

For example thinking about this itinerary. Coming from London youre train will arrive at Gare du Nord, from there is a direct metro line (4) to Notre Dame and further Denfert Rochereau for the Catacombs. For this you can take the even quicker RER B line. From Denfert Rochereau is a direct line (6) to Trocadéro for visiting the Eiffel tower and further the same line to Arc de Triomphe. From the latter a direct line (2) back to Gare du Nord, however some walking is needed to the entrance of this station.

From Arc de Triomphe you can use metro line (1) in case you have time left to see something of the Champs Élysées, place de la Concorde, Louvre etc. to line 4 or the quicker RER A to RER B for going back to Gare du Nord. It needs some time to get used to the system, but using it at least a few times it will save time, money and is fun to do too.

Even more great info.

So after reading some I think I will do a more circle tour. Actually starting at the farthest point for my points of interest. I will start at the Catacombs since that is what I want to see the most. Travel to the Eiffel Tower then on to the Arc de Triumphe, and Notre Dame. Maybe this route I will get the busier attractions out of the way. Leaving me closer to the train station at the end of my day. I may make a few other stops, but this way I am. not zigzagging all across town.

Thanks again. You guys are the best.

Piling on with TC. If you go to the Arc, then take the time to ascend. Not only great views and photo ops, but watching the traffic below is highly entertaining.

I would go to the Eiffel Tower but would not waste time to go up.

The Arc de Triomphe is great. Go up.

Maybe go to Sainte Chapelle for the amazing stained glass?

The Orsay is small and packed full of superb expressionist art. You could see so much in two hours. I would never visit Paris and skip the Orsay.

Taxis are great and not very expensive.