Developing countries (and especially rapidly expanding cities in them, like Nairobi) typically are not great for running. They grow rapidly and unplanned without consideration or funding for public spaces; and often a lack of pavements and horrendous pollution from old vehicles on the roads. And Nairobi is somewhat like this, though some of the newer roads have pavements, and there are many residential areas secluded from main thoroughfares where the traffic is light.
During the weekdays I do a couple of laps (each one just over a mile) around our residential area, and on weekends try to do longer runs. Whilst preparing for the Lewa Half Marathon, this was a regular Saturday-morning run with colleagues. We rotated among three different locations: a route that is on-rode around the outside of the arboretum (the arboretum is quite nice but fairly small and running within it would be restricted to just a few km), out in Ngong Hills, a town bordering Nairobi with some rarely-used tracks suitable for long-distance running (the circular route around the hills would be at least 40km so we would be dropped off by the bus and run 15 or 20km one way, or go 5km or 10km one way before turning around and coming back), and also some off-road paths up and down the actual hills (though i've not yet tried them).
Now that an excuse for long-runs of weekends isn't possible and that regular training is over, but Andrea and the kids are not back yet, I can still spend my weekends running in Karura Forest.
This is a fantastic forest in an area just out of town where the UN and many embassies are. There are two parts, the larger part has playing fields (occasionally for rent for events), a lovely outdoor cafe, and many paths for cycling, walking, running and walking dogs... it is huge - there is a 15km running route that goes up and down four of the main paths in the forest, which still leaves another two or three main paths untouched. There are some bike hire shops, a couple of playgrounds, plenty of small animals (deer, monkeys etc) and thanks to very good management, the whole forest is very safe. There is even a lady who comes to the cafe most weekends and does painting with kids (for a small fee) and there are some tourist attractions (waterfalls, caves etc).
Yesterday i went to the smaller part of the forest (there is a road dividing the two) which is less busy, and much simpler--there are no waterfalls or cafes and the lake that is probably normally there is all dried up (at this time of year). The longest running track here is 10km, and a third of that is on winding footpaths up and down in the hills which require great attention to prevent tripping on tree roots and rocks (compared to most of the paths in the forest which are wider tracks that are cyclable). There is also an obstacle course for adults (which took me seven minutes to complete) which is an added test after a long run (I did the 5km route after completing the 10km route for a more respectable distance).
Due to the altitude in Nairobi (almost 2,000m elevated), the weather is usually about 15 degrees in the mornings and evenings, and only hotting up to 25 degrees or more after 10am or 11am. There is no humidity (unlike at the coastal regions) so it is perfect for running. There are two periods during the year where it rains (and that is usually mostly overnight when it is cooler) and the rest of the year it is dry. So it is a fantastic place for running on the whole, especially on weekends, in the forest, past the animals and with a nice cafe to relax in afterwards. I suppose the only downfall is that the swimming pool at our compound is usually very cold as it is outdoors, the water is quite deep and it is not in the sun much. Overnight it loses any heat gained during the day, but as my dad has shown it is still fine for a quick dip after a run!