Castle Kriegspire - best of the castles, not too big, not too small

The Hive - being ubers by the time you reach the end is classic MM. The Queen could have been harder, but that whole last room is way dialled up in the Merge Mod, you actually have to be strategic rather than just waltz in & blast away. Check it out

Best - disagree:
Tomb of VARN - interesting but ultimately too long for my taste, esp the Water Temple where you hang around for HOURS trying to clear the Genies

Best - my other choices:
Shadow Guild Hideout - I love this dungeon - almost my favourite with the Temple of Baa. If you didn't lose the Prince of Thieves, you might even miss it. Cutpurses are pretty lame for opponents, and the loot is meh, but it has more mechanical goodies: doors that open differently, and the floor tiles. And the ultimate reward is a four-way teleport room to some non-Town Portal maps, where you can plop a Lloyd's Beacon and suddenly your travel options have opened up hugely

Dragoons Caverns - surprise packet for such an early area. Bigger than first appears, hard-hitting enemies and the slime area where you have to use entirely different tactics

Temple of the Moon - small with a simple little puzzle but a tough final room protecting the Druid promo

Hall of the Fire Lord - something else you might miss with the only quest given inside. Like Corlagon's Estate below, you have to keep re-checking areas that open up as you explore

Temple of Tsantsa - just cool. Like Corlagon & Fire Lord, you have to keep re-checking areas that open up as you find the levers. And that final room with all the Cobras is wild for a lowish-level party

Supreme Temple of Baa - decent size, need to keep your wits about you, some secret areas to discover, and I'm a sucker for anything with mechanical elements

Worst - agree:
Free Haven Sewers - good idea, and not badly set out, but the enemies & loot are underwhelming. However, you could even argue this is on brand, with of course rats being the main things in sewers. Could have been beefed up as a Prince of Thieves hideout with some henchmen & lair loot - they improved this in MM7

Worst - disagree:
Goblinwatch. I love Goblinwatch. Not sure why, I just always have. As above, the cheesy mechanical puzzle, it's bigger than it first appears but not too big, and the hidden chainmail in the wall is a good early-game easter egg

Corlagon's Estate - I don't hate this at all. Decent puzzles where you have to keep re-checking areas that open up as you find the levers. It's not a favourite, but not on my least favourite list

Silver Helm Outpost - this will be a recurring theme: not a favourite, but doesn't deserve a least favourite. Fine for what it is

Gharik's Forge - as above. Not a favourite, not terrible. Insanity hardly matters, and again I love any kind of mechanical puzzle (the bridges)

Castle Darkmoor - yes it's large, annoying and confusing, but that's kind of the point. By then you're almost walking around smacking stuff with no concerns; this forces you to reassess. No buffs, no Wizard Eye, mapping largely useless.....welcome back to reality, my previously smug party. Not a favourite - probably not anyone's favourite - but I like that it exists, if only because The Hive is somewhat of an anticlimax. Oh and BTW, in the Merge Mod, Eyes are now immune to Dragon Breath. You think you hate it now!

Worst - my other choices:
Caves of the Dragon Riders - my god do I hate this. No quest attached, just caves and caves and caves of Dragons for those who have to complete everything. Ugh. I hate this so much