Not the most exciting place inside, but a lovely rooftop area which not all that many people seem to know about, 2 mins walk from Old St station. If it’s packed then The Red Lion is just up the road.
The thing I love most about London is the juxtaposition of urban and rural, and nowhere is this better illustrated than in Lea Valley Park. A genuine wilderness where I’ve seen everything from ponies, to a rogue Costco outlet, and all less than 20 minutes from my front door.
By far the best bagels in London, they are open 24 hours and being just down the road from my flat a bit too local. It is run by a man called Mr Sammy, who doesn't muck about with portion size. It is well worth a visit especially for their smoked salmon and cream cheese speciality.
Free natural ponds, open all year round (check online for varying opening hours according to seasons). Get an absolute get away feeling right in the heart of London, a treat if you enjoy swimming with ducks. Amazing park to enjoy a few games of cards and a walk around afterward too...
London is so vast I end up spending hours travelling on trains. They are by far the best way to travel around on and are always full of weird and wonderful characters.