My party are going to be discovering a Lost City soon. There is one particular location they're seeking, but I want to also include ruins of other locations to give a feel for how thriving this civilization once was. Also, if they go the wrong way, the other locations will contain clues to get them back on track.

So, what kind of ruined buildings would you expect in a lost city?

And what kind of creatures might prowl its silent streets?

When I think of lost city, I think of the warden (from Minecraft). Maybe incorporate a boss creature (maybe homebrew? idk) However, this is dnd we're talking about. So here's my idea for a palace with a before-and-after to get a better feel for it:

Before: A beautiful, stunning blue crystal palace. Lush emerald-colored vines dappled in blooming flowers (petunias, magnolias, more colorful flowers, ect) climb all sides of the palace. It had four smaller crystal towers with multicolored stained glass windows shining in the midst of the towers themselves. In the center, one large tower forms with aqua glowing vines revolving around it. The entire palace is studded with blood-red rubies the size of apples.

After: A crumbled, deteriorating  building climbs high in the center of the town. It is a murky brown color with hints of what used to be a shimmering blue. What looks like four towers are now shorter, very chipped, and each tower has piles of dust and ash forming at the foot. Shriveled, black vines crawl around the building, crackling horribly and turning to dust if you touched them. Large spheres that used to be rubies seemed dirty, dusty, and no longer beautiful.

I'm a jungle temple and water temple fan myself.

My favourite water temple feature is the drowning elevator. It starts off dry, and it's the main way through to the various parts of the ruin. The elevator just appears to be a tall room built like an inverted pyramid. Once it starts to fill, they see that it'll fill up and they'll drown... but there are also doors in the steps of the inverted pyramid that they can't see until the water lifts them high enough to see over the step. These doors are all large S Bends which leaves the room on the other side dry and with breathable air. Mostly it's a non-trap, but you can then throw in later malfunctions which cause it to partially drain and cut off their access to other rooms. Or else the bottom fills with sand and cuts off their access to lower rooms.

You can do a sandy elevator in the desert. Same principal.

As for the jungle, a mini-metroidvania dungeon that's full of treasure. Let the PC's breathe and puzzle it out. It's mostly about taking a ruin the PC's can't easily explore and making it easy to explore, only for the finale to have some 'obviously too strong to kill Jaguar monster' chase them through the dungeone which they just made easy to traverse, so they need to sabotage the dungeon and whatever gold they thought was safe to come back for later.

I’ll provide some suggestions for creatures:

The Sorrowsworn are all representations of various moods that might have been caused by a city’s destruction…grief, anger, fear, etc…

I’d choose one or two that fit the motif you’re looking for.

Also, ghosts!

A variety of incorporeal undead spirits that linger within the lost city would be a perfect encounter while the party is exploring the ruins…perhaps these echoes of once-living people still re-enact their last moments before their demise…only for the party to interrupt them, provoking them to combat.

You need to first explain how and where it is lost!

If the city was in the jungle then you're looking at nature reclaiming it, mayan style pyramids, and jungle monsters like a green dragon (who has claimed the gold in the city as their own), jaguars, shambling mounds, perhaps gnolls that start off seeming a small threat but it turns out the whole city is full of thousands of them, who all start howling and laughing from above as the party careens through the streets in an ancient cart pulled by a mechanical horse, for example.

If the city was lost to demonic rituals, then demons and devils may be warring in the streets. If it has sunk into a bog then crabs and bog-mummies and such may be present. If it floated into the sky then it may have constructs and weird skybeasts in it. If it's slowly emerging from the ocean it may have merfolk and other fishy foes. If it were abandoned because of a volcano then it might ave magmins and other flame elementals, if it is encased in ice then it may be host to ice elemental monsters and mephits.

For buildings, what is the city's story? Was it a sun worshipping tribe like the aztecs and mayans, in which case it'll have pyramids. Was it a trade hub, full of warehouses, workshops and market streets? Did it trade cattle or livestock, prompting farms? Did it have a collusseum? was it a monster training town, with towers where wyverns were kept? Longhouses for feasts and such, temples for contemplation, zen gardens of overgrown cherry trees for meditation, alters for sacrifice, tunnels underground for smuggling? Pick and choose as you like!

This reminds me of The Day After Tomorrow where the travellers inadvertedly break whats actually the rooftop of a mall as they trekked towards New York.

So your party finds the ground crumbling beneath them and scrambling to avoid falling in before shining lights down there to discover an ancient stairway thats rotted and decrepid but looks like it might hold their weight with evidence of further levesl down below.

Imagine travelling down what is essentially a townhouse interior perhaps make it an ancient library or government building holding ancient records that are too fragile but there are what looks like glass panes on the wall holding maps of the interior or panthlets written in some ancient languaged detailing events from back then when this building was in use and still inhabitaed.

Perhaps even a painting, portrait or even a photograph of the exterior of the building giving them an idea of the surroundings back then.

Could have ghouls, rats, even spiders and ghosts reliving their last moments for the party to witness maybe leading them to the next part of their quest?

I've been contemplating stealing parts of the story from the game "the forgotten city"

Spoilers for those of you who might want to play it, and haven't yet (if thats the case, get on it, it's brilliant)

Taken from Wikipedia:

"The full game begins with the protagonist waking after being rescued from floating down the Tiber River in Italy. The mysterious individual who rescues the player character asks them to look for her friend, who had disappeared whilst investigating nearby ruins. As the player explores said ruins, they are sent towards the era of the Roman Empire in the now-restored city. As the plot progresses and the player continues exploring it is elaborated that the city is under the conditional protection of the gods, where if anyone is to commit sin, all citizens of the city would be equally punished and turned into gold in a system referred to as the Golden Rule (originally Dwarves' Law). These gold statues, depicting previous inhabitants and residents, can be heard whispering, but seemingly only by the player. The specific sins that are criteria for the Golden Rule to be enacted are not clear to any resident of the city, with numerous records of contradictions. The player is able to re-enter the portal they had entered from and restart the time loop if the Golden Rule is ever enacted, allowing them to keep both physical and mental objects such as important items and information."

The partys goal would be to stop a person who is going to commit an affront to a god. Meanwhile, they themselves can't commit any sins, or they will start the incident that kills the entire town in the future.

In the present, there would be statues in the town, which is petrified people.

So the monsters would be something that can petrify. Maybe homebrew something.

If you can spring for it, get Dwellers Of The Forbidden City on Dm's Guild or similar.  It's a great resource for look and feel of a forgotten city in a remote jungle.

Above ground real life inspirations: Mayan Ruins, Pueblo Cliff Dwellings, old west ghost towns, etc.

Quote from CaileynRothenel >>

 

Imagine travelling down what is essentially a townhouse interior perhaps make it an ancient library or government building holding ancient records that are too fragile but there are what looks like glass panes on the wall holding maps of the interior or panthlets written in some ancient languaged detailing events from back then when this building was in use and still inhabitaed.

I've always wanted to do something like this with an existing subway system in a world that's built around the Post-Apocalyptic Future trope

There could be magical "echos" of people that repeat the same actions on a loop.  They're invisible until some kind of attunement happens, and then you can wash your players with a thriving city full of spectral people going about their lives in a minute long loop.  (To keep the party from going crazy, maybe have a magic item that they can engage with, when they want to see the loop)

A fun idea would be to slowly lead them to the specters that actually hold clues to the history of the city.

Chernobyl 

Maybe one of the magical echoes isn't on a loop, but also can't seem to see the party?

Quote from reignarrows >>

Maybe one of the magical echoes isn't on a loop, but also can't seem to see the party?

 Ooooohhh, that’s really good!! And it can really be a tension-filled revelation 

Model it after Catal Hyuck.

Atlantis.

A lot of Tomb of Annihilation deals in lost cities: they have Omu plus a few others who's names escape me right now. Those are great models to base a lost city on. 

Take a look at Pompeii, Macchu Pichu, Knossos, Petra and the like. BBC Travel recently had an article on a series of underground cities in Turkey, with above ground villages for daily use, hidden entrances and caves etc for when invaders came