along

The preposition along is used before nouns like road, river, corridor, line: words that refer to things with a long thin shape.

• I saw her running along the road.
• His office is along the corridor.

To talk about periods or activities, we prefer through.

• through the centuries (not along the centuries)
• all through the journey (not all along the journey)
• right through the meal

Note the special use of along as an adverb particle in expressions like Come along (= Come with me) or walking along (= walking on one’s way).