A spike trap has been created in your workshop...
Both of these F-Series geomorphs feature a large (18x18-foot) pit with spikes in the bottom. Geomorph F7 has a solitary pit almost completely filling a room with three exits -- doorways, not doors; there's the narrowest of ledges (maybe a foot wide) around the edge of the pit. The rest of the geomorph is fairly ordinary.
Geomorph F8 has an 18x18-foot pit filling a 20x20-foot room; on one side of the pit is a door. The rest of the geomorph features a twisty passage filled with three smaller spiked pits as obstacles. One section of the corridor, with pits on either end, contains two chambers.
At the GM's option, the large pits may have enough room to walk between the spikes, if the adventurers very carefully lower themselves into the pit. There should be a slight chance of spiking themselves while doing so. The smaller pits are mean to have a tighter grouping of spikes, so they will need to be jumped over or otherwise negotiated without descending into the pits.
There will be another pit-themed geomorph tomorrow, at the very least, although I'm not sure which idea I will go with.