most visited city
What is the most visited city in Bolivia?
In response: I'm going to assume you're asking which Bolivian city is most visited by foreigners. To give you an absolutely correct answer is impossible. It's hard to tell because Bolivia isn't known for keeping great statistics and the institutions that maybe do keep statistics are many (Ministry of Tourism, Chambers of Commerce, Hotel Chambers and others and they don't necessarily coordinate well with each other).
However, I would venture to say that in terms of tourism the answer would be La Paz. Tourist attractions and sites in Western Bolivia have been aggressively promoted for decades and most tourists still visit Western Bolivia (La Paz, Lake Titicaca, Uyuni Salt Flats, Death Road, etc. etc.) much more than Eastern Bolivia for which very little promotion has been done, in comparison.
Even though there are dozens of beautiful places and tourist attractions in Eastern Bolivia, they just aren't as well known by foreigners (changing that is BoliviaBella's mission!)
However, Santa Cruz also receives hundreds of thousands of visitors per year (especially business travelers) and especially during the month of September when it holds the largest Expo in South America, so it might be a toss-up (or will be within the next few years as Santa Cruz is now Bolivia's most populated city).
That's why I said at the beginning that I'm going to assume you mean "foreign visitors" because nationally I would probably say Santa Cruz receives the most visitors (most of them immigrants who then stay to live here) per year.