The Mont Tendre is only 1679m above sea level, but it can be a challenging hike for your fitness - depending on where you start. I did this walk in May an took a long route of 24km and in October (15,23km).
The hike does not require any specific technical knowledge and is suitable for everyone and all kinds of mountain dogs.
I would recommend to pack hiking sticks, enough water and a little picnic to enjoy at the summit (or a bit below, because the peak can be very windy!).
24km - approx. 6,5hrs
For the long trail, start in the little village Le Brassus. There is a car park, as well as a train station, so you can easily reach Le Brassus.
Make sure to follow the trail (which is not perfectly marked at the beginning!) towards Les Combes. It will be useful for you to download the GPS track to make sure you find the trail!
The first part of this trail leads through a forest and also grassland. After a while you will reach a lovely plateau with a constant great view of the highest peaks of the Jura Mountains. The trail is gently sloping uphill through the plateau and you will reach the top of Mont Tendre after round about 3 hours hiking.
To get back down you can choose the same trail or you can follow the trail first and afterwards take the bike route no. 3. (That's the route on the GPS track!).
This makes the trail a bit longer, but if you prefer not to do the same trail, I would recommend this. But of course, feel free to choose which ever trail you prefer!
15,23km - approx. 4,5hrs
This trail is a lot shorter and even a bit easier. Anyways it's beautiful and worth it as well! Especially, as the trail is marked pretty good and you can follow paths, instead of streets.
Start from the Hotel/Restaurant at Col du Marchairuz and make your way towards Mt. de Bière Derrière, as soon as you leave the forest you will reach a beautiful plateau with little paths going across the grassland.
After round about 1,5hrs you should have reached the little Cabane de Cunay with a great view on your right hand side! (Don't miss it!)
The summit of Mont Tendre should be reached within a bit more than 2 hours during this hike.
This time I chose the same way back, because I wanted to make sure to reach the lovely Hotel/Restaurant on time to have enough time for coffee and their vast choice of delicious homemade cakes!!