With modern technology, you have explosives and landmines.
Landmines already have a proven history of being lethal centuries after being placed. You could use fragmentation weapons, which would more or less leave the Temple itself unharmed, or you could just have an 11,000 lb bomb instead of a rolling boulder trap. Best case: the adventurer makes it to the treasure, and then is atomized immediately and without warning. Worst case: the bomb goes off prematurely, taking the treasure and structure with it, thus preventing the removal of the (intact) treasure.
This is an especially good strategy since many explosives of that age no longer rely on electrical signals, as those have decayed long ago. Instead, the merest suggestion of movement is often enough to set one off, meaning that its trigger is literally tied to the explosive itself.
This also has the potential benefit of being reusable. If cluster style munitions are used, not only is the explosive extremely lethal itself, it has a tendency to spread some of the unexploded material around the trap room(called UXOs). This behavior occurs anyway despite cluster weapons not being specifically designed to do so, meaning trap weapons like these could be designed to last a much longer time, with them also designed to sling UXOs deliberately and in a more calculated manner. So as long as you have some of the original mines still left, you have a sort of self healing minefield. 523
One adventurer could stumble upon the place, trigger three mines and be killed, and the UXOs would spread to cover the same area and kill another adventurer 50 years later.
In terms of ancient technology, I'll exclude magic as it tends to be able to generate plenty of its own handwavium anyway. One of the best ancient strategies is stealth. Placing traps will prevent access to the treasure, but doing so means that any survivors or casualties will be tipped off to the potential value of this ruin. Besides, no self respecting Tomb architect places traps willy nilly.
The ruin being inconspicuous and in a remote place will go a long way to preventing the treasure from being found and will help the traps last longer. (Even the mightiest fortress or the cleverest trap will not last forever against a sustained assault.) Having a fake treasure room with a few traps and a significantly less valuable treasure is a good way of faking out adventurers into thinking they have already found the treasure. As for secret doors and fake walls, its almost better to adhere to K.I.S.S. Instead of secret doors, just wall it up solidly. Adventurers cant find a secret passage if there isnt one. Most people won't bother mining through the wall if its plain, thick, and they've already found the "treasure".
Besides, 6000 years later when your <PERSON>-y self decides to go and retrieve the treasure for whatever reason, youll have a strong knowledge of the traps and a few walls won't really hinder your progress if you know where to dig. 164