The Roundhouse was built as a steam-engine repair shed in 1846, and then became a warehouse before falling into disuse for 25 years and reopening as a performing arts venue in 1964 hosting acts like Jimi Hendrix, The Doors and Pink Floyd. It was redeveloped between 2004-2006 and is one of my favourite music venues in London; it’s a beautiful building, has a great sound and isn’t too huge so feels fairly intimate. Some highlights for me this year were The Flaming Lips, David Byrne & St.Vincent and the Timepiece installation by Conrad Shawcross.
If you want a peaceful day out of the busy city, Highgate doesn't really feel like London. The cemetery is interesting and peaceful, there's a tour of the old half which is definitely worth the money. Karl Marx, among others are buried there.
The Princess Louise, was a Victorian Gin Palace, with mirror and tiles galore, segregated seating and extraordinary urinals. With pints of beer just over £2 you're laughing. It gets packed so we come for a lunchtime pint.