For this story, I declared the following locations:

• The European alien city is on the Rhine near Dusseldorf, Germany.
• The Chateau de la Tour Rouge is at the confluence of the Seine and the Yonne, in Montereau, France. This fits the description and approximate location as depicted in The White Mountains.

I declare that a Tripod at normal pace can cover one kilometer in ten seconds, or 360 km / hr. I base this on visualization rather than any science or math. I also base this on the fact that I imagine a Tripod is 150 feet tall.

I got the distances between locations using on-line maps. On-line maps give driving distances rather than direct distances, but Tripods can travel in a straight line, so I subtracted a bit from each distance to compensate for this.

The European alien city (Dusseldorf) to the Chateau de la Tour Rouge (Montereau) is about 500 km. Therefore, a Tripod at normal pace could cover that distance in about one-and-a-half hours. In this story, the characters take twice as long to make this journey, each way, because they are being careful.

The European alien city (Dusseldorf) to Bayonne, France is about 1,150 km. Therefore, a Tripod at normal pace could cover that distance in just over three hours. In this story, the characters take twice as long to make this journey because they are being careful.