Isla del Sol
Inca legend says that Viracocha, the bearded god who created the universe, emerged from the waters of Lake Titicaca and created the sun at this location.
The son and daughter of Inti (The sun God) were sent out of one of the caves on the island with a golden staff. One of the siblings, Manco Cápac took this staff across the water and found Cusco between the mountains. He decided to start his Inca empire there. This of course is according to legend. In reality, Cápac probably lived in the region of Cusco instead.
The life in the island is tranquil, there is no noise, no motorized traffic and no rubbish on the streets (which is rare for Bolivia).
This island is very much on the beaten track of the backpacker scene, and equally popular with bolivians. Every day hundreds of people are shipped to the island; don't expect a nice and quiet non touristy experience. Doing the north-south path gives you some moments to contemplate whatever you wish to contemplate.
The only conventional way to get to Isla del Sol is by boat. Numerous tour companies operate full and half-day excursions from Copacabana. You can make reservations at the agencies, or just go down to the waterfront around 8:00 or 1:00. It's also possible to catch boats from Yampupata at the northern tip.
The people on the island clearly understood the cash opportunity of tourism and you will need to pay multiple times to visit/hike the island. It costs 15 Bolivianos to see the north end of the island, and an additional 15 Bolivianos to walk from the north to south end. It costs 10 Bolivianos to enter the south end of the island. (prices as in jan 2017)
You may spend a night in Challapampa, walk to Yumani the next morning and return from there to Copacabana by another boat.
Recommend leaving your large backpack with a hostel in Copacabana as getting up the inca steps in Yumani is hard work at altitude.
One way boat ticket to the north costs 20b.
There is also a boat leaving Copacabana at 1:30pm to the north and returning in the evening.
The last boat back to Copacabana from Isla del Sol is at 1.30 pm from Challapampa and at 4 pm from Yumani. Of course you should verify this information as schedules change.
From Yampupata local boatmen can take you across to Isla del Sol for 20 bs per person in a rowboat or for 150-200 bs per group of up to 7-8 people in a motorboat. A stop at Isla de la Luna can be negotiated.
Note that the people in the highlands are known to be rude. They are well used to trying to hike prices up for tourists and get angry if you don't buy anything from there. It leaves a bit of a bitter aftertaste to the beautiful experience of hiking the island.
There are no motor vehicles on Isla del Sol. It might be possible to rent a donkey.
Unless you're spending the night on the island, your itinerary will be basically determined by the boat tour you arrived on. Frankly, the half-day tour is barely worthwhile as it consists only of a brief stop at the southern end and most of your time will be spent on the boat.
A full-day tour will take two hours to get from Copacabana to Cha'llapampa, two and a half hours to see the museum and make a round trip hike to the Rock of the Puma, three hours to take the boat to Isla de la Luna and back to the Inca Steps at the town of Yumani, and two hours for the ride back to Copacabana. You can also choose to hike from the Rock of the Puma back to Yumani (three hours) and catch the boat from there. (Decide on this when buying tickets, as the boat fare to Isla de la Luna adds just a bit to the cost.)
Again, Yumani has the best offerings. Challapampa has some restaurants where you can get soup+trout for about a small 20 Bs. Challapampa could be good for lunch if you are coming with the morning boat and staying overnight on the island. Many places in Copacabana will sell you a lunch box, convinient for daytrippers. The few shops around have limited stocks, -fruits are mostly bananas and apples.
Yumani is growing fast and already has a lot of tourist facilities. There are some basic alojamientos in Challapampa and Challa. The cheapest hospedajes start at about $2usd per night. At those prices expect basic conditions, everything is pretty clean and decent though. Camping should be possible many places.
Ch'alla, the often-ignored village in the middle of the island on the eastern beachside, also has a couple of hostels to offer. They are situated right on the beach, with the most extrordinary view on cordillera real (royal mountain chain).
Be aware of attacking dogs who wanna bite. In case use your backpack for protection and be assertive. Asserting your dominance will, in most cases, have the dog back down.
Isla de la Luna is easiest visited from Yumani, by renting a boat.