we can focus on a couple of locations, first of all, a small but strategically important city, topmak line, a second defensive line, and then a third defensive line around the city itself. also in ukrainian media, there are reports that russia is removing civilians from topmak in order to further fortify it. we can understand that if we look here. furthest from the front line we have artillery positions, then a trench network. just, then what are called dragons teeth. these are concrete obstacles, designed to stop tanks in their tracks. also aimed at tanks are ditches, dug out by vehicles like this. and you can see an anti—tank ditch in this fortification is the very first line of defence. so, that's one location. a second that bbc verify has looked at is on the crimean peninsula, which was annexed by russia in 2014. this image comes from the west coast of crimea. you can see dragons teeth again, running up the coast of the black sea. you can see further north, a bunker, and also this trench. bbc verify estimates that runs for 15 miles along the coast. there are also piles of wood to