I typically homebrew and my campaigns generally have grand scope in mind (PCs need to find a several piece item across a wide area to stop a demon summoning) and I feel that I am missing out on the smaller things that make places (towns, cities) memorable. Things that in the next campaign bring back memories of the previous time the players were there.  So I am looking for some ideas for a coastal Viking type town. Any ideas or suggestions are welcome.

This is what I am talking about.  New ideas are welcomed.

The Jarls hall is made under the shell of a gigantic dragonturtle shell.  In years past the natural warm springs in the area fed into the sea creating a natural feeding place for the dragonturtle.  When it passed the local natives created a town in the area and used the turtles shell as a roof.

Before the turtle came there was a race of people who used the springs as a natural bath area (think romans). They created a city/town in the area.  When they moved on/were defeated by someone /died off...the turtle moved in.  Now the ruins of their settlement is below the current Viking village.  The current temple is built on the ruins unbeknownst of the catacombs below it.

What else can I do to flesh out this town?

The best advice I can give is to think of it like a real town... how do its people make their living?  Its coastal, so maybe they fish?  If so, there could be a huge, open air fish market, where fish-mongers hawk their catch and the whole area smells of seafood.  Maybe there's an army of gulls that loiter around the area seeking scraps... this could be either comical, or menacing (all these thousands of birds, watching, waiting...).

Or maybe this town is where the vikings build their longships, and there is both a large shipyard, and a thriving timber industry.  In that case, maybe the people recreate with festivals where lumberjack games like log rolls or ... i dont know, pancake eating contests are held.

Basically, take the fantasy hat off for a moment and imagine its a real place, and think of the industry and infrastructure such a place would have, and the culture that would develop around it.  Very quickly, the place with develop its own personality... hopefully a memorable one for your players.

Nice, thank you.  Both ideas are great (town based around fishing or ship building)!

This would lead me to think that the docks/wharfs are a busy place.  Fishermen who benefit from the warm waters attractions and the coming and going of their wares to the construction of Viking ships in the port.  This is great.

Possibly there is no close forest...so transport of logs and the manufacturing of planks is key.

What about the ancient ruins...other than underground unexplored places...what can we do there?

Magical nexus? Possibly a ruined tower that was an ancient mage tower (1000 years ago).  

What about inns and taverns... holy buildings...ideas?

Letterkenny, watch a lot of Letterkenny and run all your towns like Letterkenny and watch them come to life.

How much of a problem are you looking for from the catacombs? Is it a good place or an evil place? Not every burial place needs to be evil.

Are you looking for a burial sight that the town uses and knows about or are you looking to have the place be unknown and undiscovered?

Are you looking for the catacombs to be a place for the black market or thieves guild? Will you use this as a plot point in an undead scenario later (vampire/Lich/cult summoning something)?

If this place is undiscovered what will the PCs be looking to find there? Ancient civilization magics or contraptions/automatons or a gateway to another world like the Feywild or Far Realm, or Shadowfell?

Is this location the source of the fair weather and good fishing grounds by being consecrated ground to a particular deity?

You could just plant a few vague rumors about the history and see what your players may come up with.

Think about what makes irl places you’ve visited memorable. You’ve got one big idea in terms of monumental architectue — you can’t think of Paris without thinking of the Eiffel Tower. Art can be another version of that, the Trevi fountain in Rome, the Washington monument. Having industry is important, but it’s not usually something visitors particularly notice, necessarily. 
Other street level things can be good, a food the area is well known for: Chicago pizza, vs. New York pizza, Philly cheesesteaks. Some foods might even be exported, wine from some town is popular everywhere, then they visit that town. Speech patterns, not necessarily accents but words, like people in Boston saying “wicked.”

To really hammer it home, give them a history check as they enter the town: with a DC 10, you’ve heard the wine here is very well known.

• Any town/city frequented by sailors will need boarding houses and taprooms for the sailors. (The poorest drunkards would get hung over a rope in an alley to not sleep in the piss on the streets. Hence why they woke up “hung over from the night before.” 😉) There will also likely be entertainment (gambling/dancing halls), and a brisk business in “the world’s oldest profession” (if you catch my meanin’). That means disease, which means healers.
• And of course there will be storehouses for suplies and people to fix boats and nets.
• Fishing villages will need processing plants (to smoke or salt their catch); and port towns will need stevedores and warehouses, pro’ly a brisk market trade too where people would come from all over.

All’a that👆means it’ll pro’ly be a noisy place. And also likely rowdy and probably will have a criminal element. What’s law enforcement look like?

Now, onto the more “human touches” of any community:

• What do the people eat? Coastal towns will be fish & seafood most days, and every family will likely have a prized fish stew recipe handed down through the generations.
• What do people burn? No forests but lotsa mountains means coal, which means soot (lots of soot). Or if they are near a bog they might burn peat (which means stoned people).
• What are their local markets like?
• What colloquialisms do people use there?
• What’s the local fashion?

Oh, and then there’s the smell….  Of the 5 human senses, smell is most closely associated with memory. So what’s it smell like?

Everyone has given great advice so I'm just going to throw this out from the DMG where you can get some additional flavor for your town

https://www.dndbeyond.com/sources/dmg/adventure-environments#SettlementsTownsVillagesCities

Also, Ex Novo is a city/town-building dice-chucking game that I've used on many occasions to create various locations within my homebrew adventure.  If you want some depth and uniqueness to your game check it out 

https://sharkbombs.itch.io/ex-novo

Thanks for the feedback this is really helpful.  This is what I am thinking based on your feedback.

A coastal medium sized town on a cold northern sea that has been built on the ruins of the remains of an ancient civilization.  The Ancient civilization was attracted to the place for the natural springs in the area which feeds into the northern sea.  When the civilization passed (part of the overall campaign mystery) the abundance of fish in the area brought a dragon turtle to the area for the easy hunting.   When the ancient turtle passed the area once again was claimed by the wilds only to be settled once again, many years later, by human Viking like clansmen.  The shell of the turtle was converted into the roof for the Jarls grand hall and the ruins of the ancient wizard tower and temple were repurposed for the clan. 

Over the years the plentiful fishing opportunities has brought the town fame and renown for its fish market.  Merchants travel to trade their wares for a special delicacy fish that is abundant in the area.  The stew made from the fish is known throughout the area.  The easy fishing has brought other fishermen to the village over time and now the docks are rather large and a substantial warehouse/storehouse business has burgeoned.  The air is heavy with the cries of fishmongers selling their wares on the stones of an ancient gladiatorial arena and the large flocks of gulls that circle the very busy docks.

But beneath the surface of the vibrant bustling town lies the catacombs of the ancient civilization.   While much of the ancient passageways lay unexplored, those known are used by the local black market and thieves guild to ply their wares.   Little do the townsfolk know what is beneath their feet.

Main Points of Interest

• Jarls Hall - large building built under the shell of a gigantic dragonturtle.
• Ancient tower - old wizards tower that is now used for a similar purpose 
• Temple - to the elemental gods built on the foundation of the ancient civilizations temple
• Open Air Market/Fish Market - build on the flagstones of the remains of a large gladiatorial arena (ancient civ held gladiatorial games)

Obviously there will be taverns and inns and other businesses that support the fishing industry.  Plenty of plot ideas that can be used here.

Thanks for the help team, it is always good to bounce ideas off people.  Any other grand ideas? and what do you think of the above?

Think about the size. if it is like the city of brass, Waterdeep, or Sharn, then you need some districts for diplomacy. This would also have to include areas for the following armies of the diplomats/royalties to rest at. Such grand cities also needs a ton of security. A trade hub is known for its security else it would never have become a hub if security were sloppy. Have multiple markets, just like in cities such as NY you have ethnic areas and different product at the different areas depending on the people living there. Have a Chinatown, or in this case a dwarf-town. Or if it is a town much smaller than a city have it be homogeneous only having a single race living there.

Viking were rather multi culture for their time. You could have monsters being a part of the landscape. Maybe the town is inhabited by Giffs. This is where the merchants comes to get their Giffs for their missions, so it is also a training ground for their shooting and explosives. Sounds memorable if it is done right.

Maybe there is a secret tortle cult that believes that the dragon turtle was actually a god and that he will soon be resurrected. There might be a large amount of friendly tortles sitting around doing tortle things and generally being nice to have around. But they are a quiet group and nobody really knows them well. They are actually scheming up a plan to bring the dead dragon turtle back to life, threatening the safety of the whole township. That tortle playing a ukelele the party passed in the marketplace is actually an evil cultist bard who believes he will sing the song of life, calling his god back and destroying the whole town. The elderly tortle that slowly walks through the town with his head buried in ancient tomes is actually researching dark eldritch rituals that will cause the dragon turtle to rise from the dead and ascend to god status. That tortle who spends most of his time in his shell, sleeping on a street corner is dreaming of the rise of the doom turtle.