What kind of plane of existence are you thinking about ?
Is it a elemental plane?
Is it in space?
What kind of environment will you meld this castle into?
What kind of castle medival, japanse, europoean, ?
I would really decide on a genre and go with it for your references to help hone in on something as opposed to keeping your self so wide open 
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Do you already have a post apolocypse reference in mind ?
Mad Max? Water world? etcā¦
So many options so little time. I am always a fan of the the genere type
I couldnt help but to mention Bioshock hereā¦ under water , steampunkā¦ lots of good inspiration. Keeping in mind that this weeks video says keep it real if your using reference. But you could get inspiration for maybe some designs from other concept art :).
Maybe look at a time of the day for a less busy port city early morning dayā¦ And look for some markets, bazaar referencesā¦
not yet! I have been looking at war torn cities for inspiration. I am leaning towards Mad Max and Hunger games! 
Dont forget
I am legendā¦9ā¦ Final Fantasy: The Spirits Withinā¦ pick a maze runner movie
So many options!! soo little timeā¦ I cant wait to see what you put together though.
My idea is create a city to understand depth and color, I want to bring gothic or fantasy elements. Like in Castlevania or even Lord of the Rings. Ireally need help with pretty much of everything with environment design, sorry!! !
Early morning is actually a great idea. Thinking of that I found some really cool screenshots from Anno 1800 that catches that mood.
I love anything and everything science fiction/fantasy. Iād like to create a futuristic city market that is bustling with energy, a more vertical design because of the sheer amount of shops needed to keep up with the booming economy. Maybe even some mobile shops (Iām thinking of the floating restaurant in The 5th Element), however I do not want to end up with a cyberpunk feel.
Iād like to incorporate a lot of mechanical things and a lot of designs that harmonize nature and technology. I really love the beauty of the futuristic rendition of San Francisco from Star Trek, and would like to create that sense of scale while also capturing the small interesting details in such a busy world.
Hello, everyone!
All of your ideas sound super cool! I canāt wait to see everyoneās final work!
For my idea I want to create a post-apocalyptic swamp area - like a world that was once civilised and full of technology but now destroyed by radiation. Iāve got the swamps of Louisiana mixed with atomic waste in mind.
I am in love with where you want to go with it. I am a huge fan of castlevania. So much rich history,mythology, and imagination.
Cant wait to see whqt you drum up. Keep in mind i would look into some more of its historyā¦ may e watch the new castlevania animation on netflix and take a gander at vanhelsing the movie for sonething realishā¦Gotta keep it grounded in some reality to make it believeable.
Glad i could helpā¦ hope your references are easy to find. Keep in mind basic shapes will really help at the start. Dont get lost in the weeds[details]
That sounds like a lovely idea. What inspired this?
When you mention futuristic cityā¦ with a virtical design i thing starwars meets the 5th element. The part where bruce willis character dives to the lower city to save leluā¦
It probably wouldt hurt to throw a firefly reference in here either. Theres a subtle quailty in the show that could give you a example of the types of characters that frequent it.
Last thought i have is the new minority reportā¦ cell phones in hands. Magnetic cars ā¦ and interactive displaysā¦ hmmm
Its going to be interestingā¦ how would you show the toxicity.?
Creatures?
Bioluminesent plants?
Swamp thing meets maze runnerā¦ 
Cant wait to see it
What Iād like to focus on in this course is the more general importance of story ā the one āroyal roadā, in my opinion, for escaping the trap of ābeen there, done thatā in concept design.
Iāve recently been inspired by the work of Simon StĆ„lenhag, a guy I think really nails the place of story:
The distillation of his approach: Take the familiar and juxtapose upon it the unfamiliar; and ensure your characters have a fleshed-out backstory.
To this end, Iām thinking of trying out his approach in telling a story about a John Carter-esque female astronaut working her way across a landscape that resembles something she left, but just skewed 45 degrees. A little vague, I know, but thatās where the inspirationās been taking me the past few days.
So far iāve been thinking of including some mutated creatures, maybe with teeth or eyes all around their body. I might take a leaf out of Bloodborneās book or even the Last of us. iām definitely going to include some neon colours as well.
canāt wait to see your concept sketches!