Ahmad BarclayAre you the kind of person who likes to spend hours exploring #HistoricalMaps of your neighbourhood? This might be exactly the thing for you... https://bothness.github.io/ons-basemaps/
BafpundIf you're interested in a country other than the UK, here are some more historical map viewers:
Palestine https://palopenmaps.org/
Ireland http://geohive.ie/
USA https://ngmdb.usgs.gov/topoview/viewer/
Various countries/cities http://davidrumsey.georeferencer.com/compare
Trento (Italy) https://timetravelmaps.github.io/trento/
Geneva (Switz) https://www.ge200.ch/carto/
Maarten Lambrechts
Jonatan Hildén