Apparently, it's not very large, or the quality isn't very high, considering the conclusions drawn.
Added 1 minute ago
Let's compare the speed at which the hero moves during the first week for different Castles:
1) Castle - 6/7 (griffins, archers/valkyrie archers)
2) Rampart - 7/8 (elves/ivory elves)
3) Tower - 6 (gargoyles)
4) Inferno - 7 (dogs)
5) Necropolis - 6 (ghostly skeletons)
6) Dungeon - 6 (harpies, miner troglodytes)
7) Stronghold - 9 (tyrannar dogs)
8) Swamp - 9 (flies)
9) Fortress - 7 (grandmothers)