Eles são de 10 pés. Você pode usá-los como estão (e perder a sensação de que o castelo é grande ) ou redesenhar os mapas dividindo cada quadrado em quatro.
A aventura 5e usa os mapas antigos para o aventura original nos anos 80.
Naquela época, os quadrados dos mapas eram de 10 pés:
D&D had its roots in wargaming. The older books used to tell you to measure out movement in terms of inches, with 1 inch of movement representing 10 feet of simulated in-game dungeon.
You had 10-foot squares because of that 10:1 scale conversion. This was also important because then you could convert 1 inch of movement into 10 yards while out in the wilderness, compared to 10 feet while inside a dungeon.
Also, there was the temporal component to consider: because the smallest representation of time, which was the combat round, was 1 minute long, you sort of had to have larger squares because you didn't need the fine-grained granularity of 5-foot-squares if the lengths of time assumed to happen within that round was so long (1 minute) in the first place.
As for how many persons would fit in a square, older D&D editions suggested that you could have two, or as many as three, man-sized humanoids fit across a 10-foot corridor.
I'd also like to note that it wasn't exactly 3rd Edition that caused the shift in scale. The Combat and Tactics supplement for late-cycle AD&D 2nd Edition, part of the books that are sometimes called "AD&D 2.5e", was the one that started explicitly tracking squares, started using 5-foot squares instead of 10-foot squares, and reduced the combat round to 10-15 seconds rather than 1 minute segments.