Each time the hole is opened does it always open to the same space? This would mean that it could be used to transport objects. For example, can I open the Portable Hole, fill it with water, close it. Then in a few days open the hole again in a different location and have a swimming pool?

The description mentions a person stuck inside trying to get out, but does not say anything about using the hole to store/move things.

Quote from JamesGames >>

...can I open the Portable Hole, fill it with water, close it. Then in a few days open the hole again in a different location and have a swimming pool?

Yup! It's unclear whether an empty Portable Hole always opens to the same space, but according to the description it does always open to the same space if it contains something:

Folding the cloth closes the hole, and any creatures or objects within remain in the extradimensional space.

Have fun filling up your new pool. Just make sure you don't suck up a crocodile in the process, because it might beat that STR check and pop out at an inopportune moment!

Imagine if you could place it in a bag of holding, or another portable hole. You could carry an entire mountain range. Of course, you would have to dig up the mountain range first, to fit it in 10 foot deep holes, but you could still carry it.

WARNING: Math

So, I get that to some calculating carrying capacity by area makes more sense than weight, but, due to that most items only get a weight and don't get any dimensions for area, I was wondering if calculating for a weight capacity for the Portable hole via ratios would be a "fair" within the rules of the game. What I mean is...

Handy haversack (small pouch): 20 lb, 2 ft^3 / Handy haversack (large pouch): 80 lb, 8 ft^3 / Bag of holding: 500 lb, 64 ft^3 / Portable hole: ??? lb, (approximately) 245 ft^3

Handy haversack (small and large pouches)= 10:1 ratio (lb:ft^3) / Bag of holding= 7.8125:1 ratio / Portable hole= ???:1 ratio

The bag of holding's weight capacity (in ratio form) is 78.125% of that of the haversack, so would it be fair to say that the Portable hole's weight (via ratio) is 78.125% that of the bag of holding? Which is roughly 6.1035 (ratio) or 1495.3575 lbs (actual).

I get this is a weird question, and I'm sure using exponential functions would give a more accurate number, but would the place holder of a rounded 1500 lb be a "fair" weight capacity for the Portable hole?

Quote from Theran_Baggins >>

...and I'm sure using exponential functions would give a more accurate number...

So I asked my professor for some help with solving this via an exponential function and we came up with the function of (weight cap. of area cap)=(41.136)((1.040)^(area cap.))

So, in sort, the weight cap.=612,900.799 lb (or about 306.45 TONS)

...

So I think until WOTC gives an official answer, its probably safe to assume you'll never need a weight limit for the portable hole.

So I did a thing where there was a Skull on a Crimelords desk. My group was looking around this guys office for anything weird. (They were there for a letter but decided, "why not loot the place.") The skull had 1 ruby eye and a black cloth stuck in the other socket. They took the whole skull. Then later, took the ruby and sold it. But they threw the skull away... with the black cloth... which was a Portable Hole... with 13,000GP in it. This Crimelords whole stash was in that skull and the ruby was a decoy. They still don't know.

That's Frigginn Hilarious.

In Dragon Heist, my players used a portable hole to clear out the 500,000 go from the vault, stuffed in a pocket, and walked out.

How do you get something out of the portable hole?

The only actions described are those to open and close it, not the storage or retrieval of items from the extradimensional space.

As it’s supposed to be 10 feet deep, what you need to do to get that special item in amongst the piles of loot inside the hole?

Lots of space for GM rulings I guess

Option 1:L a ladder inside. Problem solved. Since weight but only volume is a point of concern with what can fit, then you should be able to fit at least 1 ladder.

Option 2: Place the hole on a vertical surface and walk in. This might cause a bit of a mess depending on how things are placed within so be sure to pack carefully.

Option 3: Carry a rope and piton. Place hole, place piton, attach rope, climb in, grab item, climb out, clean up.

Here is some quick info for our non-american users.

Its 18 Cubic meter, it fits 18 000 L of liquid
It is also 2.8 m wide, 3 meters deep.

Apologies for the correction Agamendor, but 6' in diameter is more like 1.8 m - typo?

Similarly that 6' diameter circle when unfolded would have an area of approx 28 square feet (2.5 square meters) giving a volume of 280 cubic feet (7.5 cubic meters.) That's 7,500 litres or approx 2000 US gallons.

Hope that helps.

I don't understand how I would get one in-game or how much it would cost.

That's entirely up to the DM's discretion. 5e encourages the treatment of magic items as creations of a lost art, so you could reasonably interpret the sale of magic items as a specialty market like fine art; maybe a nearby major city would have auction houses to look into. As for price, magic items are not given firm prices; it's usually within a suggested range that's determined by the rarity of the item. As a Portable Hole is a rare magic item, it could be anywhere between 500 and 5,000gp, or something else even, depending on DM fiat.

https://www.dndbeyond.com/sources/dmg/treasure#MagicItems

Since this does not specify item retrieval i can only assume the magical person of the group now has the task of mastering a spell of retrieval for anything in this giant hole. On the flip side it is also theoretically possible to weaponize something dangerous by catching it in the hole then releasing it later as a 1 shot super attack of sorts like unleashing a small lake or explosion of toxic/flammable gas and or various other methods of releasing lethal stuff via this hole.

In an auction house I would probably have them roll for luck for crowd interest on this or similarly powerful item. 1 being some obscenely wealthy person becomes unhealthily obsessed and bids any amount against you and 20 being nobody is interested and you pick it up nearly free with everything in between being a bit of a range.

Roughly how many skeletons could someone fit inside this thing

Quote from Caden_brownfield >>

Roughly how many skeletons could someone fit inside this thing

 According to the math I remember reading somewhere around 193.

I see what you're planning you little necromancer