I go hiking in the mountains every weekend.

He is good at water skiing.

The headwaters of this river are in the mountains.

Mr. Mizukami is my best friend.

The headwaters of this river are in the mountains.

Mr. Mizukami is my best friend.

We often have picnics by the river on weekends.

We often have picnics by the river on weekends.

We have a picnic by the river every weekend.

My keys are inside the house.