Notes on this puzzle
Skyscrapers #5212 is a 5×5 city: every row and column holds the heights 1 to 5 once, and 11 of the 20 edge positions carry a clue. No heights are given inside the grid; the edge clues do all the work.
There is 1 clue of 1 around the frame; the first cell beside each of them must hold a 5. On 2 lines the two opposite clues add up to 6, which fixes exactly where the tallest building stands. The top edge carries the most clues (4). 9 edge positions are blank, so parts of the grid are solved from the inside out.
Where to beginTry row 4, column 1 first: its row and column clues decide it without any other help. Remember that a clue of k keeps the tallest building at least k−1 cells away from that edge.