_{This puzzle is a part of the Monthly Topic Challenge #4: Cross-*non*-words}

Skyline’s higher half
mirrored – an ideal pangram
and but a poem. (5)

The reply to this crossword is the unclued 1-Down, a landmark whose prime half is represented by the blue squares. In order to fill it you have to determine what the numbers 1 to 7 imply and why each single enumeration is just too lengthy for its corresponding entry…

Across
2. Dormant Javanese volcano and deserted nuclear energy plant website (5)
4. Walking with _________, first in a collection of documentaries (9)
7. Mercury crater named after a Nineteenth-century American novelist (9)
10. Barry _________, loser of the 1964 US presidential election (9)
12. Indian various medication system (8)
14. Soap opera that debuted on the identical day as Channel 4 (9)
16. Direct present mills utilizing commutators (7)
18. ______ Hill, feminine Australian composer (6)
20. White Star Line ship, later Gülcemal (8)
22. “The higher wow”, per Urban Dictionary (5)
23. Small, typically domesticated lizard (6)
24. Follower of Network or British (4)
25. Squirrel’s nest (4)
26. Nose pimple brought on by extreme ingesting (3-7)
27. Constellation containing the Spare Tyre Nebula (4)

Down
2. Pondered deeply (5)
3. Touch via a mutual border (4)
4. Yes album earlier than The Yes Album (4,3,1,4)
5. Wood-cutter after the tree has been chopped down (5)
6. Enyaq producer (5)
7. Pointed finish of a hook, or a fish caught by it (4)
8. Anatomical homologue of the human ankle in a horse (4)
9. Genus of duckbill eels (12)
11. Escher lithograph that includes a compound of three cubes (9)
13. Saint Paul’s function as writer of Galatians, Romans and others (8)
15. Component of an inner combustion engine pushing the consumption/exhaust valve (6,3)
17. viz. (6)
18. _______ Aouragh, Dutch anthropologist (7)
19. Genus of the black-winged kite (6)
21. South Korean League of Legends participant at the moment enjoying for Rogue (7)