Buses leave from opposite Mercado Centenario in Iquique, cost 3.000 Pesos and take 1 hour to Humberstone. Beautiful to see they leave on certain times independant of the amount of passengers after having lost some hours of my life for waiting for trufis to be full in La Paz for going to Tiwuanaku. You get thrown out on the wrong side of the highway but there is a pedestrian bridge over the big street and after 10 minutes more there is the entrance to Humberstone where the tickets for both sites- Humberstone and Santa Laura- are obtained. Currently they cost 6.000 pesos p.P.. There are tours offered in Iquique for 35.000 pesos half day Humberstone & Santa Laura and full day Humberstone & Santa Laura and some desert oasises like Pica further away. I would definetely NOT recommand these, as they're much more expensive for transport, guide and some food and they tear the focus from this WHS away. 3 hours is NOT sufficient to see and digest the Humberstone and Santa Laura sites. We have spent 5,5 hours in Humberstone and 1 hour in Santa Laura and have rushed a little bit. You can easily spend the full day here from 9 a.m. to 6 p.m. if you want to read through all the information which you will find mainly in Humberstone. Between the two sites it's a 25 minute walk on a signed pathway. You will have to walk back for cathing the bus to Iquique from the opposite side of the highway. Luckily some Chilean visitors on the parking took us back for free after asking them.  
 
I find the site quite comparable to the Sewell Mining Town from the experience. It's also an abandoned, industrial site with a ghost town where workers had lived which is situated in Chile. This site is about the nitrate production from the caliche which is found here and once was the basis for 90% of the saltpetre used in the world mainly for fertilizers. After the discovery of a synthetic way to produce fertilizers the production out of the caliche became inefficient probably because of transportation matters as one of the reasons and caused the closure of the sites Humberstone and Santa Laura in 1960. Afterwards the sites became a national monument and later WHS. The museum in Humberstone is one of the better museums in Latin America. Some rooms have too many information and some only display artifacts without further information but there are good English translations available and a lot of visible displays to discover. I liked the exhibition in the Pulperia (grocery store) the most. The Urban sector of Humberstone appears like a Western Town during Siesta underlined by a very small amount of other visitors. There is a lot to discover and I would recommand to take a picture from the numbered map at the entrance to not get lost or miss anything. The industrial part I found a bit spooky. You're alone between rusty and huge remains of the factory which make sounds in the wind and appear like thed could collapse anytime soon. Some explaination signs tell you how the process went from Caliche to crystalized salpetre however I found it hard to connect it to the remains I have seen. The mirador gives a nice overview of the organised pattern of the urban part.  
 
Santa Laura appears similar to the industrial part of Humberstone 
 The urban part is mainly ruins. The part in which the caliche gets mixed and heated with the liquids to extract the salpetre is huge and can be seen from many kilometres distance. Again I find it a bit spooky running around here alone as with the partially heavy wind in the desert the buildings seem to talk to you. The only real danger though would be falling parts of the construction or falling or tripping on the floor full of industrial remains though.  
 
I can really recommand visiting the sites as they have been histotically very relevant roughly a hundred years ago and give a good impression of what was going on here. Today they contain a good museum and are still an impressive appearance in the desert.