No one knows what it looks like:

1 Corinthians 2:9 King James Version (KJV)
⁹ But as it is written, Eye hath not seen, nor ear heard, neither have entered into the heart of man, the things which God hath prepared for them that love him.

Jesus says “in my Father’s house are many mansions”:

John 14:2 King James Version (KJV)
² In my Father’s house are many mansions: if it were not so, I would have told you. I go to prepare a place for you.

John in vision described the “holy Jerusalem” out of heaven as a city made of “pure gold, like unto clear glass”, “and had twelve gates”, “and the foundations of the wall of the city were garnished with all manner of precious stones”, with a lot more detail described in the verses below:

Revelation 21:10-21 King James Version (KJV)
¹⁰ And he carried me away in the spirit to a great and high mountain, and shewed me that great city, the holy Jerusalem, descending out of heaven from God,
¹¹ Having the glory of God: and her light was like unto a stone most precious, even like a jasper stone, clear as crystal;
¹² And had a wall great and high, and had twelve gates, and at the gates twelve angels, and names written thereon, which are the names of the twelve tribes of the children of Israel:
¹³ On the east three gates; on the north three gates; on the south three gates; and on the west three gates.
¹⁴ And the wall of the city had twelve foundations, and in them the names of the twelve apostles of the Lamb.
¹⁵ And he that talked with me had a golden reed to measure the city, and the gates thereof, and the wall thereof.
¹⁶ And the city lieth foursquare, and the length is as large as the breadth: and he measured the city with the reed, twelve thousand furlongs. The length and the breadth and the height of it are equal.
¹⁷ And he measured the wall thereof, an hundred and forty and four cubits, according to the measure of a man, that is, of the angel.
¹⁸ And the building of the wall of it was of jasper: and the city was pure gold, like unto clear glass.
¹⁹ And the foundations of the wall of the city were garnished with all manner of precious stones. The first foundation was jasper; the second, sapphire; the third, a chalcedony; the fourth, an emerald;
²⁰ The fifth, sardonyx; the sixth, sardius; the seventh, chrysolyte; the eighth, beryl; the ninth, a topaz; the tenth, a chrysoprasus; the eleventh, a jacinth; the twelfth, an amethyst.
²¹ And the twelve gates were twelve pearls: every several gate was of one pearl: and the street of the city was pure gold, as it were transparent glass.

The “The wolf also shall dwell with the lamb, and the leopard shall lie down with the kid” and “the lion shall eat straw like the ox” the Bible says:

Isaiah 11:6-7 King James Version (KJV)
⁶ The wolf also shall dwell with the lamb, and the leopard shall lie down with the kid; and the calf and the young lion and the fatling together; and a little child shall lead them.
⁷ And the cow and the bear shall feed; their young ones shall lie down together: and the lion shall eat straw like the ox.

There is “a pure river of water of life”, and “the tree of life, which bare twelve manner of fruits, and yielded her fruit every month”:

Revelation 22:1-2 King James Version (KJV)
¹ And he shewed me a pure river of water of life, clear as crystal, proceeding out of the throne of God and of the Lamb.
² In the midst of the street of it, and on either side of the river, was there the tree of life, which bare twelve manner of fruits, and yielded her fruit every month: and the leaves of the tree were for the healing of the nations.

Heaven does not have “death, neither sorrow, nor crying, neither shall there be any more pain”:

Revelation 21:4 King James Version (KJV)
⁴ And God shall wipe away all tears from their eyes; and there shall be no more death, neither sorrow, nor crying, neither shall there be any more pain: for the former things are passed away.