Forest Hill is a residential neighbourhood in southeast London, largely off the tourist trail but worth a visit for one reason: the Horniman Museum. Frederick Horniman was a Victorian tea trader who amassed an eccentric and wonderful collection of natural history specimens, musical instruments, and ethnographic objects from around the world. The museum, set in pleasant gardens with views over London, is free and includes a famously overstuffed walrus — a taxidermist's error that has become the museum's mascot.
The Dartmouth Arms is a good pub nearby. Forest Hill is easily reached by Overground from central London.