Pucará de Tilcara
Set on a hill above the left bank of the Río Grande, this fortified, pre-Inca pucará (settlement) is the best-preserved of several in the Quebrada de Humahuaca and the only one that can be visited. Its different areas (some of which have been rebuilt) can be clearly discerned. Allow at least 90 minutes to walk around the site, where an estimated 2,000 Omaguaca once lived, worshipped, and kept their animals. On your way out, turn right at the entrance to the fort for the Jardín Botánico (Botanical Garden): inside you can admire a large array of cacti and other plants. Don't miss the chance to strike the Piedra Campana with a mallet disguised as a stick—true to its name (Bell Stone) it rings like a bell.