The tunnel that continues on winds downward for quite some time, with small rock falls, dripping water and moss, but no natural light. After a small bit of time traversing the tunnel, (since the stables), the party will hear small noises, (if they make a perception check of 25), such as foot scuffling, pebbles tumbling, a cough, something along those lines. Up ahead is a small patrol of drow/rogue elves. Make the level appropriate to the party level and add as many in this patrol as you feel necessary.
Small things to remember:
1) No natural light, so who ever has the light source may be a great target.
2) The hallway, at best, is 10 feet across with the ceiling being only 10 to 12 feet high. This will effect combat.
3) At best, two people can be up front.
Tomorrow, the small village under the ground.