Copacabana

Copacabana, bordered by the Titicaca Lake, owns one of the most beautiful church of Bolivia. This church shelters the famous skin changing color Virgin.
Copacabana is a turistic harbor to go and seesight the sun and moon Island.

Titicaca lake

This a non-salted internal sea, 3800 meters high, with clear water. The light is marvelous, and things contribute to reinforce your idea to be in a unreal world. The Sun Island has Bora Bora beaches (except for the water temperature).
in my opinion, the Moon Island doesn't worth to be seen.
Both have Inca ruins, but they are really ruins. So, go for the lanscapes and not for Inca ruins. Enjoy the long time you need to sail the lake.

Coroico

I went to Coroico by the death road with a down hill mountain bike rent in La Paz. That was great. The falling down lasted severals hours and 3500 meters. The first part is tared and quite safe. But the second one, becomes a path. Dug in mountain and with trucks are sometimes wider than the way. On the way down, you have on your right the moutain and on your left ... nothing except a true death whether you fall.