I’d wondered why Mauritius had these very steep mountainous areas that gave way to flat or at least uniformly sloping plains. And why were the mountains so often topped by jagged peaks. Now I could see it. The mountain ranges more or less circled the perimeter of the island, a few miles inland from the coast. They formed the most massive volcanic crater, over 25km across.
How many eruptions of lava over the years had gradually filled up the main crater space I do not know, but it must have been hundreds. The mountains had formed and eroded, forming that characteristic jaggedness. And the lava once it had filled up the crater had spilled through the weaknesses to make a series of lava plains, each one gently dipping down to the sea. The southern one was wide and short; the larger longer ones to the north where I lived, and from Moka into Flacq, and from the central valley down past the airport to Mahebourg produced these bulging lobes of coastline which gave Mauritius such an interesting geographical shape. And yet another spilled out between several little mountainous outcrops to form the western plain. At one time the crater edge must have been at a pretty similar height.
That was possibly why one of the tallest mountain, Pieter Both at the northern end of the crater, was almost the same height as the tallest point, Piton de le Petit Riviere Noire, at 828m. The difference is that the Piton is surrounded by a massif of mountains that means it never looks that striking, whereas Pieter Both rises solitarily almost from sea level without a break.