Lol. that sounds like the DM wasn't prepared for you to jump into that portal.Can't say I've had particularly interesting experiences with it yeah. I think the best bit was probably when we went around the barn of a hoarder vampire that was just chock full of insane stuff, including a magical ice box with a portal to a tundra... But that exploration was soured when the DM decided to send a re-skinned Clay Golem at us, despite its CR being WAY too high and it having one of the most BS mechanic I can think of. Because he felt he couldn't challenge us otherwise (when he was the one who wanted us to roll for stats...). Maybe you could count meeting some quirky shop keepers in various cities as 'Exploration' but that feels more Social to me, even if you're 'exploring' the city.
That right there tells me quite a bit. When I DM, I try really hard not to think in terms of challenging the players and I try not to make it personal if my players win. I mean, one session, my group absolutely curb-stomped a behir in its lair. They used good tactics, what am I supposed to do other than say congratulations.
This may be a decent example of how to handle exploration, at least how I handled it. It was an abandoned underground temple complex (i.e. dungeon) that had become the home of a behir. The group decided to explore it. It had several rooms related to temple type stuff. The behir was the only real threat in the complex, and it lay in a deeper area.
The important part of the exploration was the descriptions of charred dead bodies, of charred streaks on the floors. If there is a behir lairing here, it would make sense that some other interlopers would have fallen prey to it, and evidence of this activity would be apparent. This creates a feeling of forewarning, the players knew something was up. They didn't guess behir, but thought dragon or similar. It informed their choices on how to explore and informed their decision making. The results of their choices were what enabled them to get the advantage against the creature.
This highlights several elements of exploration.
1. The location was a cave hole in a hillside. It contained a creature that was at least equal if not a greater challenge than the party would handle. This was a placed location on my map, and the players ran into it.
2. This behir lair existed here and would exist if the party were 5th level, 1st level, or 20th level. (Monsters and locations don't scale to party level).
3. The location was designed such that there would be evidence of the behir's existence. A smart group of players should have been able to make a guess as to what may be in store for them. A 1st level party would have enough information to nope out of the location and move on.
4. Exploration of the first few rooms provided clues to the challenges to be discovered in the later rooms. I described the streaks of burned stone neutrally. It was up to the players to decide if that information was relevant and what it meant.
5. There were a number of choices in how to proceed. The party elected to split and explore two different passages that connected together later. This was what allowed the group to minimize the behir's lightning blast while at the same time flanking it from two sides.
Agree.I think it also works best if you're not pushed for time and have enough to go where your interest is piqued and not just have to push on to the next plot point at all cost.
Drawing from my experience in something else, a good Exploration experience has to be the Hoenn games in Pokémon. For exemple, north of Mossdeep City is Shoal Cave. The place is completely optional, you don't need to go in there to complete the game, but doing so will you find Snorunt and Spheal, two rare Ice Types. Furthermore, if you visit at low tide AND high tide you can collect items to have a Shell Bell made for you, a held item that allows Pokémon to recover a little HP whenever they inflict damage. Shoal Cave is tucked away in a corner of the map, in the water heavy portion of the game. The game also has a completely option town that, on its own, doesn't actually give you much, but it's an unusual location with its own special sprites and lore associated with it.
The point you make about time is really good...
Tomb of Annihilation has this problem. It gives you a blank hex map with several 'dozen'? locations all sprinkled across miles and miles of land to be explored and discovered. And then it tells you that you have like 7 days (or whatever) to find the Tomb or the world will end. Seriously?
It is a perfect example of what I mean by using exploration incorrectly.
I also think your example from the Pokemon game is an excellent example of using exploration correctly. A location that is completely optional. The players have no real compelling reason to go there other than curiosity. But if they do, they can discover an interesting element or boon or treasure. It is exploration as its own reward.
Several things need to happen in your game to make that possible...
As you mentioned, the players shouldn't have to optimize their actions against some outside pressure. If your campaign relentlessly pushes them to move against the plot, they will consider any such locations as a waste of time and energy. They will sacrifice curiosity for diligence.
You got to have some places to be just pure reward. I know it is a feeling that everything has to be a challenge and combat, but sometimes you just need to put a magic sword in a tree, no strings attached, to be claimed by whoever finds it. If you show this stuff is possible, then you will encourage more exploration.