For a nice, relaxed day of Sunday ruins, today Chris, Pascale and myself went and visited the ruins of Tiwanaku, which are just an hour's bus ride out of La Paz. Tiwanaku is the home of the Tiwanaku culture, an ancient people that built themselves an empire upon the altiplano of Bolivia, long before Inca times, and that were most likely the ancestors of many modern-day Aymara-speaking Bolivians.
On the Peruvian side of Lake Titicaca, they speak Quechua — just like in Cusco, and in most of the highlands of Peru — the language of the Incas. But here on the Bolivian side, they speak Aymara, the language of the altiplano ("high plains"). Apparently, the lake is not just the border between two countries. It's also the border between two languages, and between the two ancient cultures behind them. Looks like I won't be needing my Quechua phrasebook anymore (not that it helped, anyway — Quechua is downright impossible to learn).