Dating back to the Liao dynasty (around 1120), the pagoda in this little-visited temple is reputedly the oldest structure in Beijing. The octagonal tower stands at a majestic 57.8m tall with 13 eaves, though much of its exterior statuary has crumbled away. Tianning Temple is a 25-minute schlep from the subway, so you might consider taking a taxi.
The temple is a modern reconstruction, active with worshippers and monks. The chimney stack on the power station next door makes for a compelling photographic contrast.