I discovered a secret tomb under the ruins on that Island in Champs Les Sims!

There is an adventure linked to that tomb.  (EDIT:  Not an adventure, but a game play way of getting there without teleporting across or using a boat to get to that island.)

There is a place where I often send my sims to catch butterflies and fish at the little fishing hole. It's out in the world. Your sim needs Pangu's Axe which they find in China. If they have the Axe the sim can smash the boulders near that spot with the butterflies. There is a set of steps revealed under those boulders. The tomb is big and complicated but you will eventually come across a dive well that takes your sim to that tomb under that island.

I have a series of videos that do walkthroughs of the World Adventures Tombs.  

In The Isla Paradiso Bunch Episode 35 you can see the boulders they need to smash to get into the tomb that leads to the tomb under that island.  Later episodes of that video series will show how to get through that tomb and travel to the tomb you found under the island.

You can see the exact spot and the boulders that the sim needs to smash with the axe in this video at about the 3:08 position.

Location of boulders a sim needs to smash to find a large tomb in Champs Les Sims.

I remember that place. It's a great place to harvest money trees. 🤑

Yes I noticed that! They had money bags on the ground underneath them like fallen fruit!

Congratulations! Cool find! I've often wondered about what's under the island ruins because they hint at something don't they, but my sims have never had an adventure there either ... and they've had the axe with them before. I suppose if you had a sim with one of the adventurer life time wants and focused on the World Adventures for long enough you'd end up finding something under everywhere. There's probably something under practically every square, except for some residential houses - there's some with adventure tombs underneath, they're annoying to access aren't they and sometimes it seems having the inappropriate happiness reward doesn't work.

Anyway, be swimming in sims there eh.

karritz  What adventure is linked to that tomb?  I've never come across one in my several years of playing with WA content and having my sims travel to France, but I also haven't done every single adventure available.  I'm curious as to whether I've missed something fun.

For anyone else doing this tomb, be sure to bring something to sleep in, especially if your sim wants to stop and harvest the plants.  Even without that, it's an all-day experience.  I typically send two sims, one to do the tomb-related activities and the other to harvest grapes to use for nectar later on, especially since you can't buy the rare grapes without a level 3 visa and it takes a while to grow more of them.

It doesn't take all that much, or too long to get to level 3 visa if you go hard at it with a couple of people, I mean sims, the teamwork thing. I usually try to get someone to that soonish so they can have a holiday house there - much better than base camp! I suspect its one of the adventures that comes up later, possibly triggered by having the axe.

Which rare grapes are you meaning btw? The red, blue, pink and green one's? You can get those in the big tiered front garden of the house at the end of the riverfront, and some around the ruins on the island, and then grow them at home. They're definitely all there by day 3 of a minimum trip. And a pink diamond somewhere in on the winery side of the river ... have to really look for it.

I wish my procrastinating would hurry up so I can play.

DivinylsFan  I know it's easy to get to visa level 3, which is why I haven't done all the adventures.  I don't generally grind enough to accomplish it in one trip though, and I space out the trips, so it takes a while for my sims to actually get there.

The grapes (I meant cranerlet nuala and gralladina fran, only available at visal level 3) do grow in the basement of the Landgraab estate, and probably at the abandoned house too, although I haven't checked there in a while.  But there are only a few plants each, and my sims want to make nectar while they're waiting for their crops to mature, so collecting a large quantity at once is much more convenient.  Not to mention, my sims sleep overnight on the island and get another pass through Tuatha's Garden the next day without having to travel over there again.

My understanding is the island is only accessible by swimming (which takes a very long time) or Zeneport (which means time spent building the Martial Arts skill and meditating), so it's not any better from an efficiency perspective.  And this way, they get treasure along with enough grapes to last until one of them can plant and harvest the rare grapes at home.

To get to the island, just go into map view, click to go there and the sims will automatically go there via taxi-boat if they don't have their own boat from home in their inventory. Swimming is just a romantic thing for taking pictures in stories, and doesn't take all that long and is definitely not necessary. The dark blue grapes and the red grapes are available on that island, around the blocks of ruins, as well as a few butterflies and bugs and a couple of fishing spots, and a tent or two will fit on there. There's also a couple of excavation spots. The grapes will definitely be ready for harvest by the last day of the shortest holiday. I always make my sims go there for them by rule of thumb. Whereas the pink one's they can get over at the tiered front garden of the vacant holiday house at the end of the foreshore. And of course the green, yellow and white ones, but they can be got at the winery vineyard too. To grow them at home you only need one of each, which you have to keep replanting until you get the perfect quality anyway, so if you plant more than one its too much work. Unless your sim has top gardening skills, a quick-gro station, fertiliser, and science radiation experiment thingy, but they still need replanting once or twice. Even if they don't need replanting, you still only need one because the plant produces more. 

That's been my experience anyway. I've probably got some photos somewhere.

DivinylsFan  I don't have Island Paradise active right now (installed, but I hid its registry entry so it doesn't load).  Plus, it feels a bit cheaty to just boat right up when the original intent was to make it difficult to access the island.

The Meloire (pink) grapes are available with a level 2 visa; the Avornalino (green) ones are available at level 1, I believe, plus there's a row of them at the Nectary.  Cherimola Blan (white) and Renoit (yellow) can be purchased from the food vendor.

The issue, for my gameplay at least, is that Cranerlet Nuala (red) and Gralladina Fran (blue) are only available with a level 3 visa, or in one of the locations I listed, and they're rare and so take a level 7 gardener to plant them, AND they make excellent nectar.  So my sims are ready to make wine that includes these grapes before they can grow them, or at least before they have a garden full of these plants.  (I don't like to plant more than one until I get to Perfect or at least Outstanding, as it seems like a bit of a waste.)  Collecting ~20 of each means more interesting nectar recipes, and more money coming in, while my sims are experimenting as they learn the skill.

I think you can also use the Eyes of Horus (World Adventure) or the Teleportation Pad (base game) to teleport there.