Logic Masters Deutschland e.V.

The rules:

Normal sudoku rules apply.

Each digit in the grid represents the height of a building in its cell. Taller buildings obstruct the view of shorter ones behind them. Clues outside the grid give the number of buildings visible from that vantage point in the clue's row or column.

Marked cells are smaller than orthogonally adjacent cells.

Click the image to solve it on Sudokupad.