Many have said some brilliant episodes here but I have a massive soft spot for Hartnell's Planet of the Giants. Today the concept of being shrunk down isn't all that novel and we've seen it a bunch of times, but they do some quite clever things with the episode and there is some really great framing shots.

For its time, I think it shows the ingenuity of the teams that were making the show. Even to this day, it is rare you find an episode that plays with the 'Space' part of TARDIS like this one did.

I'd love to see a modern take on this one.