superlative view; magnificent scenery
A literary, somewhat old-fashioned expression for a view so beautiful it could be called the finest under heaven. Often used in travel writing or poetic descriptions.
The view from here is truly a superlative view.
天下 (tenka, 'the whole world' or 'under heaven') + の (possessive particle) + 景 (kei, 'view' or 'scenery'). Literally 'a view under heaven', implying a view that is the finest in the world.