Even if you are not planning to continue to Bolivia, even if you just entered from Peru and are eager to reach Santiago, I do strongly recommend reaching at least the limit between Chile and Bolivia in Tambo Quemado. Few places in the world allow you to climb from sea level to well over 4km in less than 200km of well-paved road. The morning buses leave at 9:30am and costs 7000CHP. It would be a sin to take the night buses, as well as uncomfortable, since they leave after midnight in order to arrive at time for the pass opening in the morning.
Most of the way climbs through a very arid landscape, with occasional llamas and cactuses, but 150km after the departure, you will arrive to Putre, the Tarapaca Region’s capital. It is well worth visiting the place since it retained the colonial features of previous centuries, including a church of adobe, called Iglesia de Putre, dating back to 1670. The international bus does not stop here; if you want to visit, you should take a local one from Arica’s terminal.
The spectacular limit is divided in two different areas: the Chilean and Bolivian outposts are some 10km from each other, and each one provides different views. The Chilean side name is Chungara, which is the name of the neighboring lake as well, and both are at 4844m above sea level. The deep-blue water practically touches the immigration building ,and friendly birds will allow you to take their pictures while you wait to your stamp. Beyond the lake, there are two beautiful volcanoes of an almost perfect conical shape that are called Nevados de Payachata and which occasionally smoke.
Once in Bolivia, the pass is called Paso Portezuelo de Tambo Quemado. Beyond it, you can clearly sea the highest mountain in Bolivia, actually a silent volcano called Sajama that rises up to 6,550m above sea level. From here on you are on the Bolivian Highlands, and if you are heading to La Paz, a slight decent along the plateau is all what expects you. The way between Arica and La Paz longs about 8 hours, and the morning buses include breakfast and lunch.