At 1,440m above sea level, the 'Highest Tower' was considerably lower than advertised, and is in competition with the seven towers in the Huangcaoliang area for the title of 'highest tower' in Beijing. The seven towers of Huangcaoliang look to be somewhere in between 1,400m and 1,600m above sea level, and we'll be taking the GPS out there next time we visit to find out for sure.
Setting aside the discrepancy in height, this was still an excellent hike: the trail was easy to follow, and the views were excellent.
Statistics: 4 hours hiking (5.75 hours start to finish) over 14km; start height 880m, highest point 1,440m, lowest point 680m (where we had snacks and drink after the hike). Estimated 1911kCal burned.